Another thing to consider is, the idea of pulling extras for the tank can actually slow the run down rather than speed it up. If you're taking excess damage grabbing those extra mobs, not only does the tank have to stop his own dps to pick them up but so does the healer who has to heal you. While tank and healer dps arent a match for actual dps classes, reducing them or outright eliminating them because they have to pick up your adds or heal you, can end up resulting in no time gained or actual time lost, especially if someone (or everyone) dies because of the overpull.