Never, NEVER ult first. Save it for when he innevitably grabs you and tosses you off the map. When he does, spam your ult button - it will stop your momentum the moment he lets go, and bring you back to safety.
You have much more mobility in your kit, which you can use to stay safe. Also pay attention to other enemies in the surrounding area. If you can eliminate them, you can gather up your teammates and make the rest history.