if you eat your adc, your team will lose dps in teamfight. of course it is good for getting your adc out of mass cc, but how well will your team hold out when its a 3v5 while tahm and the adc is running away? disprove by 1st reply, looks like he is a free cleanse in teamfights
if you want to eat the enemy carry, you need to find a way to apply 3 stacks and get right next to him while not get peeled off by tanks
his q is really unreliable stun in teamfights. again, you need to apply 3 stacks 1st before getting stun, and it only it 1 person and the 1st person, which is usually the tanks. also shield is really bad vs poke, if poke does more than you can heal and you are on low hp, you cannot get stacks for shield or anymore heal
he looks like a beast in lane and setting up ganks