Well tbh, I think THM should be the dedicated Healer/DeBuffer since its AOE cone is defintely much suitable for healing, while THM also has more of an upper hand when landing debuffs with succession.

CON on the other hand, defintely hits a bit harder when nuking and has the dedicated "Ancient Magic" spells. But it also has those status effects removals that belong to a WHM, so I dont know ; ;