Noticed this today, as game stability has improve from some hotfixes. Healing powers are locked(unusable) when a critter is under the reticle! this was very noticable in a delve with a load of fleshflies by undead pops, i couldn't use mutagen as the reticle was resting over the swarm. tested a bit more outside and rats were interfereing with heal use too, both R staff and templar.