I've been playing this game for years, and I only just discovered a way to keep companions in almost perpetually good health...
Now, could be I'm *extremely* late to the party, but just in case there's at least one other person out there as dense as I apparently am...
I ended up enchanting a Daedric Katana for Julan that has
Sanctuary 20 points on Self for 5 seconds
Restore Health 7 points for 5 seconds on Self.
Cast on Strike
I've made similar weapons for Constance and Jasmine... Since then I haven't needed to heal them after a mele engagment.. not once!
It works great, and has no negative consequences, unlike giving them CE items.
Anyway, like I said, just thought I'd share. I was getting tired of constantly needing to stock my companions with bought healing potions or having to heal them after battles.