the positioning shouldn't be a problem if the monsters don't come behind you, which should be unlikely to happen in any dungeon. It's often easier to pack everyone to avoid patrols, to allow the healer to use holy (in case of lv50 WHM of course)

I usually come back to the group when I know there won't be any wipe threat, to ease my job if a dps take hate back. It's better to be already here instead of running after him in the entire dungeon