You have a very good point, Mendalas, but even as a healer, I'd agree: you pull it, you tank it. Sure, accidents do happen, and I totally don't mind that, but if a DPS oversteps their bounds and intentionally goes off to pull another pack of enemies and expects the tank to just deal with it, then I'm not so forgiving. Now as a DPS, I know not to try to out-tank my tank. If one gets away from him or if I accidentally pull one (Read: ONE) extra enemy, let me handle him. I can put on my big girl panties and take a few hits, if only to cover the healer/buy the tank some time to help me out.

Selfish as it might seem to let a DPS tank something they pull, it's more selfish for the DPS to overstep their tank and pull more than he may/may not have intended.