I would say he biggest flaw is that he is only as good as the rest of his team. so you need that in mind when you go into team fights. aswell as what lanes you will be ganking.
Your main targets will be the adc/apc. To either keep it from the team fights or flash Q W combo it out from cover of its team.
You will be vary depended on your grump buff to really be a treath in teamfights. since it proc torment to any one that attacks you.