Quote Originally Posted by ShadowYomi View Post
An example I run through mobs in wp hm after gaining aggro and turn around. Next thing I know I have brd and blm behind me and sometimes a whm beside me.
Similar to the lazy tank picture.
A possible explanation in WP HM is they think you are probably going to pull that group together with the next one, were running to the next group and turn around when they see you stop there to have that group of mobs killed before continuing.

Where the tank may or may not do a big pull it's best for the healer to run and arrive before the tank or not much later and be able to start healing ASAP once the tank has arrived to the place and got aggro of all mobs (but not before so that the healer does not get aggro). The tank's health may go down quickly if the healer is a bit slow to arrive in a huge pull. Same (but not of same critical importance) for the DPS since the sooner the mobs die in a huge pull, the lesk risk of the tank dying.