I did lead him on a bit, but I never expected him to follow THAT FAR. Made it a little harder to kill things though, he's an indiscriminate healer (although I should have figured that when he healed Kurzick minions...)
And yeah, I hate those NPCs that heal everyone. I remember a quest in the Realm of Torment that involved one. Since Torment Creatures make copies of themselves when they're on low health, you don't really want them getting healed up.