Careful where you point that thing

Leafmint

Just noticed something with restoration staff.
When you are in an area where you have NPCs bashing away at each other, the following can happen if you cast healing:
If you happen to heal a friendly NPC (and your range is rather big) you will draw the ire of the other NPC and it will come at you.
Had an area where I was just swamped by enemy dremora. The cause was my inadvertent healing of friendly NPCs within range of the staff.
Using a different heal solved it for me in the end.
Moral of the story... Careful where you point that healing staff.

Yam_of_the_Center

I had this problem in some city in VR Auridon, hahahaah.

I would use Regeneration/Mutagen as a type of buff before launching into a group of enemies, only it kept doing as you say, healing some NPC that is scripted to instantly die when a player character interacts with that group.

So I'd buff up and kill off my targets while the enemy NPCs would take down their friendly-to-me NPC target then come racing after me. For a while I thought it was some kind of triggered event happening after I killed a group, which was annoying as the second group often killed me since I was out of resources from killing the group I was actually after.

Eventually I learned the lesson as you did.