You pull you tank question.

[TBerry]

It's basically a difference in mentality.
A lot of people find dungeon content to be boring so they want to get it done with asap. Pulling ahead does help speed it up so it can be viewed as them being helpful.
Tanks can communicate if they don't want that but YPYT as you said, is way too extreme and def not the answer.

Nuke 'em while the tank runs ahead, try to thin them out.

... did it really never occur to any of you that the mobs die faster the less HP is left?