Its mostly just supers thought right, crowd control is mostly just a super that clears loads of Ads, and maybe a super cell, support is just a bubble with the same weapons as everyone else, at the same time I've done almost all the content in this game without having all the sub classes. Most i did before Kings Fall I hardly ever changed weapons, expect too Ice Breaker for a few bits, with Kings fall its my main load out, then ToM load out after daughters.
In terms of subclass, I change almost nothing for each sub class expect maybe rejigg for PVE vs PVP, I've never had multi builds for PVE depending on content, and its also not something you see often. Mostly its just change your super a bit e.g. if I'm DB and I need to be sneaky I'll build for that, if not just keep it inline with PVP.
When you compare this too an MMO, you can see very clearly there is extremely limited build diversity, the classes all basically do the same thing expect a super that up for a small amount of the battle, we don't really have tradition roles e.g Tank, DPS, Healer and instead everyone kinda does every again with the exception of their respective supers which again is a small part of the game time.
I think there is a lot of the MMO aspects lacking in this game, the roles of the classes is too close, they can all get similar stats, use almost all the same weapons, have exactly the same perks on gear bar things that relate too skill tree. I can for the most part have a Titan built very similar too a hunter, have the same perks on all my armour, same status, same weapons, doing similar damage, taking similar damage. This also missing out all the none raid stuff, you can open any MMO and have 100s hours of quests too do, a good deal is mid numbing and boring, but its still stuff too do, even if its go get some crap, go get more crap, it is better then people just finishing all the content quickly and moving on.