What I did as a marauder when leveling it up: Spam Overpower until 500 tp then just auto-attack and if it looks like I'll lose the enmity before the dps kills the thing I'll heavy swing > skull sunder.

That is pre 30 lvl when you get defiance and butcher's block. 3 over power and just maim/butchers block combos altered, never lost aggro like that and never ran out of tp.