Having seen the THUM ability list, there are definitely not OP. Scourge and Banish are weaker than regular nukes (kinda have to be since there is no resist for them). THUM has better "spikes" buffs, and slow, but thats about it when it comes to debuffs. I actually think that Conj has thum beat at everything.
As far as Conj's being healbots, I don't think we'll see that either. 14's not going to have 11's party dynamic of 1 tank, 1 healer, 1 support, 3 DPS. 14 looks to be alot less group specialized, and you'll see 2-3 people healing while DPSing, and alot of offtanking. All heals being AOE works alot better when damage is spread around.