Everything is the same because of the obsession with balance. Every ta k has to be able to eat that tank buster. Every healer has to be able to heal a full party..
Originally they were more diverse. Old was a defensive brick wall that could tank anything just had no dps. So it got shafted because it. Defensive tanks don't work in the pure dps meta. It's the same with whom. Pure healing power but gets shafted cos it doesn't fit in the dps meta. And all that healing power simply isn't needed.
You cannot have diverse jobs because everything is built around a present party of 2 2 4 composition. So if you have a tank that is a defensive god but no cos and duty finder puts 2 of them in the group suddenly the group's cos takes a nose dive. If that same group had 2 wins they'd be pretty much screwed in cos checks.
On the flip side if you had 2 warriors that could put out the hurt but needed constant healing cos there defense wasn't anywhere near paladins. And that party had 2 scholars that lack healing power but smash out cos. You might fight that group screwed because it's impossible to keep the tanks alive...
If you want job diversity you need to get rid of the duty finder and let players build parties around there own compositions. Pld tank well we'll only need 1 for this fight and a single whm should easily be able to keep the group alive...
Warrior tank. Ok so we might need 2 of them or a second healer to keep them standing....
Or a second hard to help with no management. It would open up party compositions a lot and allow jobs to have some real diversity
But as long as duty finder and the 2 2 4 set up exists everything will be practically the same...
Even now before the consolidation the tanks are identical.. healing a warrior on my scholar is no different than healing a paladinor a dark. The amount of healing is the same regardless. That tank buster smacks a Saladin for 30k damage. It smacks a warrior and a dark for 30k damage to. It's no different.