Adding my +1 to this topic.

Healing is especially awful with undergeared tanks. The worst I've had personally was a tank in the Vault wearing all Ironworks gear. Not even the augmented version, which is i130, but the base 120 set. The Vault drops i142 so we're talking about 22 ilvl difference. I had popped into a Vault in progress on the last boss and the previous healer had left, and I understood why when the fight started and the tank required constant baby sitting not to die. And the way the tank spoke, he assumed it was all the previous healer's fault and had nothing to do with him, and probably didn't realize that I was only able to carry him due to being geared and experienced. He's going to run a roulette again and get a healer that can't carry him and still not realize that his gear is part of the problem.

If there were ilvl requirements, undergeared players who go through the game thinking they're fine (when they are actually just being carried) wouldn't be as much of a problem.