I know ppl wont agree but rankings mean shit, you already need RNG and shitloads of other things in order to actually get proper ranks. But yeah buffing Exorcism to make it a priority to get as many as possible out would work but then we lose a stable and relatively effective holy power builder so I don't think the hard-cast Exorcism should make a comeback.
It's a known fact that blizzard likes to experiment with tier bonuses for future baseline abilities (or as talents). ToT tier 4set now looks to be one of our lvl 100 talent options, which I think is awesome. There's lots of other examples that they've done and that we can look at, our current 4set I think is extremely interesting because you can delay it for it's duration and hit it on the end if you know more adds are spawning or whatever or you can use it in a "rotation" sense that you use it when it's appropriate for single target.
Exorcism in it's current form works fine in a rotation-wise thinking. It doesn't hit anywhere close to hard enough for it to be something Art of War can proc, they can (imo) buff Exorcism so it has prio over Judgement and Crusader Strike or they can change Art of War to proc something else. DP could be an option, our current 4set could be an option. There's lots of things they can do, I personally think Exorcism as a stand alone spell is fine if you take away the Art of War part. With Art of War it's far, far too weak as we all know.