The breakdown on how parties should go.

Engaging mobs.
Tank does aoe and focuses on one target.
DPS work on that target.
If mobs disengage and go for healer. DPS with stuns disengage and chase to stun until tank picks back up.
Go back to mob tank was previously focusing.
1) Do NOT pull in front of the tank.
2) Don't stand in nono circles.

How hard is these simple steps to understand? I mean jeez people.