I really wish XIV had a talent system like MoP-era WoW. Where you have a few different skills across a few different tiers and they serve to allow you *some* degree of customization of the playstyle. People argue that the "best choices" will be mathed out and so there's usually only a couple choices that are genuinely up to preference, but I don't see anything wrong with that. It's rare that the "best choices" are the best choice for *ALL* content types. I think as long as you can justify each of the abilities or passives in a tier in some type of content, the system is working fine.
I certainly don't think we'd ever see anything like DF's talent trees, although I think they're quite lovely for the most part. People math out the best choices there, but even then there is still often a wide array of possible choices based on what kind of content you're doing or even just playstyle. Storm of Swords/Annihilator is probably weaker in general than a typical Raging Blow Fury build, but unless you're pushing top end content early in the tier, it doesn't really matter that much - you can zug zug all you'd like if that's what makes you happy. Each tree tends to have a fairly even distribution of "core" skills, "preferred" and "optional" skills. Each tree also has its share of "never take" skills, but theoretically that's something you can address with balance patches. It would probably be a lot easier for XIV to achieve that since each class is just the one class, rather than each class kinda-sorta being three in one like in WoW.
I keep thinking back to Blue Mage. Sure, you always have a certain core set of spells you use for pretty much everything, but those last 4-6 spell slots are *highly* variable based on what content you're doing, even down to the specific fight and even specific strats *within* that fight. Combined with not losing ability access for being synced down and is it any wonder that BLU players tend to greatly prefer BLU to normal classes?
Shit, they could do the specialization thing for XIV, too. Although I'm sure it'd be messy, but what if you could pick between Warrior and Berserker? Berserker is melee DPS, Warrior is a tank. Or I guess if you want to discount the probably severe amount of code fuckery, you could just have Marauder be melee DPS and Warrior is tank and players get an ability to swap seamlessly between them (while out of combat/not bound by duty) at will. Same gear is used, too. Tenacity can still function for "tank DPS", since I think it would still be dead last in gemming priority even for a DPS class because the extra mitigation on a DPS wouldn't likely ever be relevant. It would be like a more involved version of DPS stance/Cleric stance, except it'd also change up your toolset and not just your modifiers.