The trinity (or now the “foursome” introduced by games like Rift with the advent of “support/controller” classes that are neither dps, tanks, or healers) can be frustrating at times. It is restrictive in more than a few ways and presents a familiar set of problems that many of us have jumped onto a soapbox over. Especially me.
However, I love tanking and I love healing. The experiences are very different from the DPS experience. You need to pay attention to more. You need to react faster. You have more targets, more to worry about, and you are a linchpin. If you’re good and you’re DPS, well you get a raid slot. If you’re good and you’re a healer or a tank, you are fundamental to the success of the group.
The roles come with a lot of stress for all members of the “trinity”. These points of stress are very familiar to us; they’re the kinds of things that inspire young angry people to shout at strangers on Ventrilo. Either you’re short on the non-dps classes, or those that you have aren’t very good at their roles, or both.
Games like Diablo offer an alternative: no trinity means you can potentially see all of the game in whatever way you want to. You never “have to take one for the team and tank” because nobody else wants it. The stresses are fewer and smaller. The game can still be challenging, but it’s challenging only as a game instead of also being challenging in social organization. You needn’t worry about “dragon points” or “main and off tanking” when a party full of necromancers and rogues is perfectly viable.
It’s still fun too, as is evidenced by the still vibrant D2 player base, as well as anticipation for D3. But the trinity wasn’t about spoiling fun; it was about variety. We’ll still have variety in games like D3, sans trinity…but will we have healers and will they be necessary?
Are those two things mutually exclusive? I don’t know.