On top of that, Sigma was released; his Kinetic Grasp does the same thing as Defense Matrix but can restore shields and is on a longer cooldown.
Va unless you're certain she has low health.
I've seen too many players hold onto Ults for too long.
A sturdy as your teammate frees you up to play as a more aggressive.
Va players use her like.
Reaper and Roadhog are notable, as well.