Dvas ult is the easiest to fuck up. But you don't need to get a multikill on every ult. If you're about to win on payload for example, just ult on the payload, make the enemies run away from it. Or just to get the payload rolling. If you're doing good damage, you'll have it pretty fast so there's more than one chance to use it. Also, don't be afraid of orisa (just be in her face and use your missiles, usually freaks them out) or bastion. If you charge into bastion while pumping missiles and defense matrix at the same time, you get him pretty easy too. And be on widowmaker as soon as you see her, get her out of place and fuck up her momentum so she can't get any kills. And of course, dvas defense matrix can eat almost every ult so don't hesitate using it. It can eat about half of pharahs ult so do that and then charge into her while shooting. On maps where you can be pushed out of the map, don't go near the edge unless you have your charge ready just in case.