I . . . don't think incarnates even matter in this convo of who can or can't be mezzed.
It's level 50 content, end game. The End Game League you're on is making you better in ALL aspects: Damage, Recharge, Defense, Resistance, etc. Mez Prot being there via Clarion isn't a big deal compared to all the other ways your League is making you overpowered (a good thing, that's one of the major selling points of teaming in COH).
If we're talking about mez protection, makes more sense to come at from the 1-50 game, which a majority of players are going to spend their time.
Interesting discussion though.