If the tank is doing his job right, healers shouldn't really have a need to manage their threat.
And OP, yes you can teach someone to tank, but they have to want it. None of the tanking classes have overly complicated basic rotations. It's mostly the situational abilities and awareness that are things you have to think about while tanking. I never think at all about the rotation. I just mash buttons and the mobs stick to me. He needs to get to the point where he doesn't have to think about what ability to use and can concentrate instead on just watching the stuff around him and responding appropriately.
Kathy, I said, "I'm lost" though I knew she was sleeping
I'm empty and aching and I don't know why
Counting the cars on the New Jersey Turnpike
They've all gone to look for America