Not quite sure how this is being equated in this theorycraft.
So how I'm looking at it is based on an overall graph, say we list all performances for specs for the current patch, top down to the worst performing spec.
In theory, if Outlaw and Mut are overperforming (I take this as top of the list), while sub is underperforming, then in theory Dark Ranger's sub would also be considered underperforming since it is the same spec. They're relatively tied together, and shouldn't really deviate more than a couple ranks away from each other at best. If Sub is underperforming, then I would see this applying to Dark Ranger as well since it is meant to be a gauge on overall performance.
Same with MM. It can be balanced as seen fit for the overall graph, as should be the full aim. I don't see the point of just balancing it beside BM and Survival alone. Specs aren't really ever balanced among themselves outside of regard of other classes, or at least I don't see a reason for Blizzard to balance this way. Min-maxers will pick the best Spec to play if it outperforms, and will stick to the one they prefer if it doesn't perform top-tier so long as it's within reason on full graph of Specs. I mean isn't that the general meta of WoW anyways? That you should be bringing your Best spec to the raid if you're looking for top performance? Then that applies the same to playing the best class for the job and the meta demanding as such. People trying to stick with Druid healing and struggling when Shaman outperforms it completely would be part of the way the game is designed, and there's no real fixing that meta whether we factor in new classes or not. As long as these specs are balanced *within reason* I think that's the main goal here.
And just to be clear, Domination is what I'm calling the new Dark Ranger spec, it's not a renamed Subtlety. I noticed you tying Subtlety to Domination in your example, and I just want to clarify that the 3 Dark Ranger specs would be Marksmanship, Subtlety and Domination (New spec). If Sub Rogue goes down, then it directly affects Sub Dark Ranger, but not Domination or Marksmanship. And for the sake of discussion, I'm fully accepting if one spec happens to wildly out-perform other specs as long as it's all specs in the game are universally balanced within reason.
https://www.wowmeta.com/shadowlands/dps-rankings
Like in this example, you can see Afflic and Demonology are doing fairly well while Destruction is piss-poor at the bottom. Well, yes, that sucks, but that's the way Classes and Specs are generally balanced. And all things considered, Afflic and Demo numbers are pretty damn good for the class overall. I'm fine if Marksmanship underperforms while Subtlety overperforms within the same class, because the Warlock is a much more extreme example of a spec that falls to the wayside while the class itself is considered performing fairly well. And that's kind of the way we have to look at all existing classes and specs in general; not every spec is going to be viable all the time and Blizzard isn't going to be designing new classes in the future based on the idea of them having to be top-tier performance. Numbers like the Windwalker and Havoc DH are absolutely fine to me as long as people are allowed to have fun with the classes of their choosing, while the min-maxers continue playing the specs that perform best regardless of any new additions to the game.
There's two camps to this - either you are a min-maxer/power gamer, or you're an underdog. I'm not offering a solution because I don't see it being a problem. I see it exactly working as intended, and the shifts-in-power as being something Blizzard already takes into account for every class, whether they choose to tweak the specs or not.
The example I used is not the common-practice, it's going to be the outlier for a class that has multiple fantasies to hit.Druids are just the class that has a lot of readily apparent cross-spec spells, but all classes have that. Are Dark Hunters getting sprint? Stealth? poisons? Evasion? Vanish? Blind? Sap? Can they kick? Do they get one kick (Sub) and lose the other (MM)? If they are getting sprint, stealth etc., do they only have those in sub and then just have a 100% completely different spell list and tool kit when they switch specs? Do they get shroud? If so how do you balance that rogues are taking a significant utility hit by having another class able to just switch specs and bring their exact capabilities but with the added versatility of not being melee when they switch spec? If you have three completely isolated specs with zero crossover spells (which is basically mandatory to maintain any sort of balance without making two separate sub/MM specs), how do you resolve the fact that the dark ranger doesn't feel like a class, but like three different classes with completely different mechanics taped together? It's not going to feel good hitting that button and watching every single spell on your bars go away and replaced by a new set that share no mechanics at all.
When it concerns having 'no common core abilities', I think it would be sufficient to have the New Spec be the bridge.
For example, if a Spellbreaker were to have Prot Paladin and Arcane Mage specs, then the 3rd spec should be informed by that design basis. Regardless of not being a true healer, Prot has healing spells, so the Prot Spec should keep them regardless. When dealing with the Spellbreaker spec, we can then choose whether or not to carry that over as a common ability. Same with Spell Steals or Spell-shields from Arcane. That would all inform and influence the design of the New spec, and it can pick and choose what concepts to bridge together and what concepts to keep exclusive to each spec.
Base utility like Ressurections or Raid Buffs should be handled as a Class-wide decision. I'm not concerned with factoring raid-wide utility into spec balance since it should be expected that *someone* would be bringing it regardless of an Echo class. We can discuss these on a class-by-class concept. A Prot Spec would still have Blessings available for themselves, but can be retooled to be self-only buffs for the sake of maintaining balance while altering the Raid Utility dynamic. This gives some reason to still play as Paladin, without compromising any balance by removing the spell entirely or double dipping into other Class-wide buffs from other specs.
There are going to be instances where keeping Class buffs exclusive to the Core class would be beneficial for differentiating the compositions, so it's not literally bringing a 'Paladin' to the group when you bring in a Spellbreaker. You're going to get the unique properties of having a Spellbreaker in your group, and it might be not having Paladin group buffs or Ressurection, but instead you gain some other form of utility, like being able to create Portals out of combat. While it's a really loose example, I'd liken a Guardian Druid as a Prot Warrior that has raid utility of a healer. You have the Rage mechanics, the Stuns, the Charges, the Interrupts and all the survival mechanics, while being a Druid gives you the benefit of having Healer-centric utility like heals and ressurection. And as long as we consider things like Bears having shitty-heals and ressurection as not being game-breaking when compared to a Prot Warrior's own brand of utility as a Tank, then we can move forward in considering what deviations we can allow for Raid utility between a Spellbreaker and a Paladin.
I'm not trying to dismiss the argument, and I think it is absolutely valid, but I don't see it being as big of a problem when considering how deviating certain specs already are within existing classes. If we're not taking specific Class Buffs into account like Blessings, then really Ret could be considered a very different theme from Prot, with mostly the Judgements and Holy Power resource being connective tissue. Outside of that, most of the gameplay and abilities are fairly self-contained, as opposed to how they were designed in Vanilla. Instead of shared AoEs, Prot uses Consecration while Ret is designed with Templars Verdict and Divine Storm in mind. Instead of everyone auto-attack proccing, Ret is given an assortment of different Strikes and Seals to activate, as well as their own DPS abilities. The only real commonality between them is Resources, Raid Utility and the barest of Common abilities like Holy Light.
And when you place Ret on the graph, it doesn't really matter how well Prot and Holy perform for the Paladin to be regarded as a whole. Ret could be bottom-of-the-barrel DPS while they're the best Healer in the game, and that would all be defined by the Meta rather than any intentional means of making them the 'Best Healer Class' of the game. If the spec needs to be buffed, then it can be buffed.
There isn't going to be cross-polination of abilities between specs though. I'm not quite sure why you are assuming this. All Core class gameplay should be regarded as being self-contained and fully ported, 1:1. The main exceptions would be Raid utility and Class-wide buffs, which can be retooled to being self-only for the sake of balance.There's also that even if you have the three specs individually isolated, the above shroud example is just one of a bunch of balancing issues created here: outside of combat what you're describing is completely and totally broken. A class that can freely stealth around at full speed, spec swap and now have a hunter pet to tank for it and extreme kiting ability. That has access to tracking and lockpicking, that can bring sap and also bring traps if sap isn't working. That can bring shroud and heroism via pet. That can survive falls with disengage and also shadowstep upwards, directly counter stealth or make full use of it... and all of that is without even touching whatever capabilities the actual dark ranger spec brings. They also triple dip on new any potential new abilities.
Any common abilities would be bridged one-way to the New Spec. The New Spec is the bridge between the other two, picking and choosing what to carry over, what to keep exclusive.
An example could be bridging Prot Paladin and Arcane Mage as a Spellbreaker. Where do we have commonalities? Well it comes from an Arcane theme which would be encompassing the entire Prot theme, while Arcane Mage gets cosmetics for having Shields as weapons (purely visual). The gameplay of the specs themselves are fairly self-contained regardless of the classes they came from, and the connective tissue really gets pushed if you start seeing magical blue sparks come from your 'Judgements', and the iconic Magical runes above your head when you buff yourself with a 'Seal'. The resources? Arcane Power instead of Holy Power. The ability to use shitty heals? Arcane's ability to Spell-steal? Both of these can be introduced into the New Spec as a means to bridge the concepts, without actually having them cross into the existing specs.
So your example of Shroud? It would be exclusive to the Subtlety Dark Ranger as a self-only buff, *with the possibility* of being a carry over into Domination (but not likely, since it's very differently themed). All Core Class abilities should be considered to be self-contained. Any consideration of carrying this through as a Class-wide or Raid Utility buff would have be considered on a class-by-class basis, and for this example I would say this Raid utility should stay exclusive with Rogues, while Dark Rangers simply gain the benefit of a self-only cooldown for Subtlety, for the sake of maintaining spec-balance.
It would be easier. I have no doubt that it would be easier to just add new specs to existing classes. I'm simply offering an alternative that would broaden the game more than simply adding 'more of the same' when we consider how limited certain classes like Rogues or Paladins would be if they are meant to stay within the same general themes of the classes, and sticking with the Core abilities. IMO it limits the amount of freedom they have to explore new identities. It's sort of like how I feel about Covenants, where it's cool that we're getting new abilities for every class but they don't really feel like they're all that necessary to exploring the class itself. Some Covenant abilities feel like they were additions for the sake of meeting certain 'status quo'.It just seems like you would have an easier time adding like 4 or 5 new specs to classes than you would constructing this one new class that in theory is only getting a single new spec.
At the end of the day, I'm pushing for exploring new identities, themes and fantasies. I don't see 4th specs being able to properly convey a "Warden" or a "Spellbreaker" or a "Shadow Hunter" the way a new class or Echo class could. The identities are bound to the core class, and every 4th spec has to play off that same identity.