The problem is that "dispelling" isn't that easy as you just put it to be.
Both the healers have to not only make sure they don't stand together, but also make it possible to reach eachother and the warrior at the same time.
if for example paladin gets Sfuryed behind a pillar where priest can't get him and the rng runs him out in the middle away from the pillar (think nagrand arena here) the paladin will most likely die at this point.
also the fact that the healers have to avoid 3 different CC's (clone/fear/hex) while keeping up with healing/dispelling makes it really difficult.
the hardest part, as said above is the fact that a simply sfury -> fear will kill/force bubble unless the fear pathing is with you the entire game, simply because reliably dispelling is damn difficult due to how the maps/pillars are placed and the fact that if you stand together, you'll eat a sfury --> howl -> clone*3 while your pally dies.
sure there's trinkets, cd's, etc, but eventually you'll run out of 'em - a destro LSD have the same amount of CC as an affli (we dispel through ua as well if we have to), however, thier burst is a lot scarrier.
as said above - your best bet is to rush one of 'em down really fast, if you fail at that and they survive the opener, have fun trying to beat 'em.
I wouldnt say that destro/ele was scarrier, because you can dispel immolate/flame shock. But again, we havent faced any destro ones, so I can't really tell I do see your point however.
And I dont think the rushing will work at higher ratings.