Maximizing fizz's effectiveness?

I kinda main bruiser top fizz right now, and I cant seem to do much at all in teamfights. My ultimate goal is to just ult the highest priority target and gtfo before anything bad happens, but my ult always screws up and hits the 5000 health malphite who is standing right next to my target, and we end up losing the fight because I baited my team. how do I maximize bruiser fizz's effectiveness?