That's kinda right, although I feel alot of people underestimate the difference a great group makes in GW2.
We had that discussion a few months ago, didn't we? In this very thread, I'm sure.
So I'll restate the problem. For a group-oriented combat, you need:
One. Sharply defined roles that can be assigned to people (either by class, or spec, or build, whatever). They don't have to be Tank, Heal, CC, Slower, they just need to exist.
Two. Roles that complement each other (the healer allows the tank to work, the CCer reduces the load on tank and heal to manageable, etc).
Three. Roles that are highly visible. That's where the "condition applier", or "might distributor" of GW2 fails. Because if it's not visible, then the average players will not discover its existence (and, if told, will not understand its function or usefulness).
And four: Strategies based around those roles remain relatively stable for the vast majority of fights. If you need a different set of strategies for every single fight, you've lost the vast majorities of players. If you need a different set of strategies for all combination of classes, you've lost as well.
The ultimate truth is: the average player is going to learn a handful of synergies based around very simple personal strategies (tank's health goes down a bit, I HOT. Tank's health goes down a lot, I Complete Heal). Anything more, and that content is going to be "hardcore" and not available to the majority of them.