So I've played this game for a while now, and I feel like there are a number of things that come up almost every expansion and cause problems. So I wanted to point them out and maybe offer some ideas for solutions.
1. Gearing
Issue: There's usually two forces pulling Blizzard to two different sides. On the one hand you want balanced PVP where skill matters most, and on the other people want a degree of progress and customization in PVP. Separate from that, almost universally, PVP'ers want the best PVP gear to come from accomplishments in PVP.
Solution: First off, let's have a PVP stat, because I think the game hasn't managed at any point or in any of the iterations managed to do better than BC when it comes to desirability of PVP gear for PVP.
I think a PVP damage reduction stat is the better choice, with damage/pacing in PVP being balanced around two players fighting each other in PVP gear. The reason a PVP damage reduction stat is better than a damage increasing stat is because you want things in any type of gear to die when fighting each other. Too low damage is a lot worse for the game than too high damage.
I think the way to approach it is to have PVP gear use 5% of their primary stat budget and transfer it into the new Resilience stat. Resilience should then offer damage reduction equal to 3 times the value of what the same amount of primary stat would grant. So for example a PVE and PVP version of an item would be different only in the following way:
PVE Item: 100 STR + 20 secondaries
PVP Item: 95 STR + 20 secondaries + 15 PVP resilience
Where 15 resilience cancels out 15 Str.
So basically PVP geared vs PVE geared you end up with roughly a 10% net benefit to damage in vs damage out. This should make the effect limited enough to not entirely impede progress, but still sufficient to make it desireable.
Balancing should also keep this in mind, if at any point the prevailing strategy of any class or spec overwhelmingly leans to using PVE gear over PVP gear at high ratings, that could be an indication the class has too much baseline survivability (as a combined factor of their mobility, CC and damage reductions) and should be a reason to make balancing changes to that spec or class.
Finally, PVP gear should have an ILVL equal to the highest PVE Ilvl at a rating of 2200, not only is 2200 probably more rare and difficult for a single person to achieve than completing the highest level of PVE content, lowering it from 2400 means that those competing for the highest level of titles will be able to do so on an equal playing field, as they will have unlocked the highest tier of gear 200 rating before. Because of the re-introduction of Resilience and the budgeting I described, PVP gear would still be slightly inferior to PVE gear in PVE at an equal ILVL.
2. Selfhealing and mobility.
The number one thing that has bothered me in the most recent expansions is how spells like frostbolt, shadowbolt, incinerate and many DoTs seem to have zero effect in terms of moving health bars. It's often been said that damage is too cooldown based, which is true, but the issue also has to do with passive healing and shielding effects.
Not only do these spells do too little damage in the first place, that damage is also entirely cancelled out by passive healing and shielding. Basically, the bucket is being refilled at the same rate which it is being emptied when casting these weak "filler" spells, leading to a net effect of zero. It also results in making things more bursty when CDS are active because the passive heal rate is then so far exceeded that it has no time to fill the bucket at all, making it meaningless in those situations.
Passive healing from experience is too high when its at or above 0.5% of a characters health every second, and made worse when the character in question has high mobility.
In shadowlands this means I expect certain Soulbind Conduits to be problematic, for example:
Recuperator for rogues, which generates 0.5% HP per second while slice n dice is active (almost always), increased for higher levels of the conduit.
Similarly I think Tempest Barrier for mages could be problematic, granting a shield passively on every blink, going up to 15% of their maximum health at the highest rank of Conduit. Basically 60% of a healthstone every time you Blink..
Solution:
Cut down on selfhealing in through passive and instant heals, especially for mobile classes like DH's, Rogues, Monks, Ferals and Mages. Self healing can exist but it needs counterplay, like kick vs drain life. Or require a significant resource (Word of Glory) or time investment (like the old Soul Harvest 9 sec channel heal for locks in cataclysm). As a rule of thumb, cut or change any effect that works out to grant more than 0.3% of max hp/sec on a mobile class. Or over 0.5% on an immobile class.
3. Healers are too strong.
The fact that 2v2 requires dampening levels of roughly 25-60+% just for teams with healers to begin to be killable in that format is a clear sign that they're broken in general. There's no dampening in other situations so clearly if that's the amount of healing reduction required to make anything happen against them the game is fundamentally flawed.
Solution:
Healers need to be weakened. Most healers are simply far too survivable. Let things die. It's absolutely outrageous that a 20 year old game like classic has healers in a more healthy spot than BFA. They're useful, even required for successful BGS but they can actually die fairly easily too when caught.
I understand that if you're a priest facing something like a DH in 2's right now you're wondering how well such a nerf would work out. But if DH's didn't have insane self-healing combined with mobility as per the previous point they wouldn't actually be able to tunnel you down and follow you permanently with no concern for their own survival.
UPDATE (17 September):
Blizzard created an update post with a new proposed solution to the gearing problem: The idea is to make the PVP trinket set bonus improve the damage and healing granted by versatility and add versatility to every PVP piece. There are some issues with that proposed solution.
1. Itemlevel is not mentioned which is a major cause for concern. If Mythic raid gear is higher ilvl than PVP gear then any such gear with versatility on it is going to outclass PVP gear still.
As I've stated before, I believe 2200 should be the rating at which a PVPer gains access to the best possible PVP gear so they can compete on an equal playing field for the highest level of rewards (gladiator titles and above). That means that we should be getting Mythic raid level gear at 2200 rating under this proposed solution. That might pose a problem for PVE'rs if it turns out versatility is the best or second best stat for any spec.
2. Having PVP trinkets buff only damage necessarily means that damage while not wearing those trinkets is going to be lower. Since I assume PVP is going to be balanced around people wearing their PVP trinkets, that means that any form of PVP where someone isn't wearing their PVP trinkets is probably going to feel shitty or slow because nothing will die. I've always felt that for worldpvp and PVP in general its better for damage to be too high rather than too low at a baseline, which is why I suggested the PVP stat be damage taken reduction rather than a damage done increase.
To sum it up, I still think my proposed solution is still better overall. But I can see some merit in putting extra weight on PVP trinkets, since trinkets have often been especially problematic in the past.