Winston and Orisa
Winston: Don't put your bubble down as soon as you land, think of it as a way to extend your effective health. Don't focus armoured targets, wait until their armour is gone and you'll inflict way more damage. Most importantly, pick a backline target, dive, kill them, dive out, get heals, and repeat.
Orisa: Constantly replace your shield. Fortify reduces more damage while you have armour left, but as a consequence, you will also gain less ult charge. Prefire on your bubble to maximise its effectiveness. Turn your (huge) head when running away.