Isn't this class trinity a bit dated now?

[FunkyBunch]

Hybrids are incredibly hard to balance. Not only do they need to be balanced in and of themselves so that one aspect isn't completely overbearing making every other aspect useless, but they also need to be balanced with every other class.

I agree it's difficult. Do you remember how long it took Blizzard to balance Druids!? They took forever and constantly went from overpowered to underpowered. Having SE try that would ruin the game.
I do miss the talent trees though.

The only way I think it would work is if there was a second job based on your class that was geared to support (or DPS if you're a BRD/MCH) that level concurrently with your class.
EG-THM gets Time Mage support role, ARC gets Ranger DPS role
But every DPS class would have to have a support role or it would ruin the balance of dungeons and DF.