Right now, it appears that standing on a corpse is simple enough to thwart a monster casting corpse reviver on the corpse you are standing on. The animation plays but past that nothing happens. Shouldn't this behavior be punished somehow? Maybe by local, corpse-burst esque damage to the player.
I've seen anecdotal evidence that suggests corpse reviver doesn't work if a monster is standing on the corpse, either. If that's the case, then either of these two proposals would actually make corpse reviver much less useful to the monsters as it would result in the monstrous masks (et al) frequently harming their fellow badguys. Making those monsters weaker doesn't seem to be what you're intending, but I think that's the effect these changes would most likely have.