Or the healer knows that he could heal through it even if you use absolutely no cooldowns. Communication should always be the first thing to happen if you don't like how your tank's pulling, but I'm also kinda tired of the whole tanks-are-automatically-the-leader-and-whatever-they-say-is-law mentality. It's a big part of why we have so many entitled tanks. Just because they're the least played doesn't make them more important and/or delicate.