I can say there is one major upside to being a WHM: I never have to worry that my cohealer will, in some way, override my abilities.

What I mean by that is that all of my WHM regen abilities stack with another WHM. But when I play my SCH I always have that little fear in the back of my head that I'll get stuck with another SCH whose shields could overwrite mine (or I could do the same to theirs). Not a major nitpick but something I think about. Same for AST. Being in a pug group with another AST requires coordination of card dispersal and that only happens if the AST is competent.

While I don't feel that WHM is becoming more unnecessary, I do agree that they need something done to their tool kit. Maybe not something new added but existing things tweaked, such as lowering MP cost to allow for more comfortable DPS. One thing I have frequently noticed is when I DPS on my WHM to the same degree I do on SCH (or even AST), my MP goes down the crapper real quick.