I think it has its place in certain circumstances
After posting my review of Final Fantasy XIV's endgame content, a discussion erupted across the review itself and my social channels. Some of them really dug A Realm Reborn's old school use of the "Holy Trinity" mechanic, and some hated it, citing Guild Wars 2 as the wave of the future.
For those who don't play MMOs, the Trinity is basically a system that forces players to adhere to certain class standards. In Final Fantasy XIV, Paladins and Warriors "tank" (soak damage), White Mages and Scholars heal, and everyone else is DPS (damage dealers). In order to clear high level content, you must assemble an eight person crew of roughly one to two tanks, one to two healers, and the rest DPS.
If you're looking to queue up for the group finder, it can often take DPS a long while to find a group since there are so many more damage dealer classes than tanks or healers -- so right off the bat, it can get frustrating when you're attempting to put a raid together.
The other disadvantage of the system is that once you commit to leveling that class to 50, you are often (but not always) locked into that role. In Guild Wars 2 classes can fulfill multiple duties, and in some MMOs you can "respec" to slightly change from one role to the next -- but for the most part, you are limited in Trinity-centric games.
To some, this may sound like yet another reason to never play MMOs. But I still think that the system has its place in hardcore games. For one, it's easier to balance fights if you have people doing certain roles -- and thus, it's easier to make them more difficult and complex. Because everyone has a certain role and job to fulfill, fights can be designed around these roles specifically, forcing players to either get better or find new ways to top them.
The same could be said about games that lack a Trinity, but for the most part, I find those games to be easier in general because fights are designed to accommodate every playstyle at once -- which doesn't satisfy the hardcore itch for many people. So while I think we definitely could use more MMOs like Guild Wars 2 in the world, I don't mind the Trinity if the game is worth the squeeze.
What about you?