Wouldn't it be a good idea to make it so that they can not revive each other?
I just came across two of them, and they would just cast an energy dome and revive the other one whenever I killed one of them. It literally took me 10 minutes to finish them off.
What I'm saying is: They should still be able to revive any other Gremlin creature, just maybe not other Healers.
Maybe if they had to pay 1,000 energy to revive they'd be a bit more hesitant to spam it.