In coop as a support player, I used use Overstock and Team Medic. Now I roll with Team Safe and Cluster Bomb.
If one or both my buddies gets downed, I drop the Cluster right on top of them…clears out most or all enemies without harming my mates, then I go in (not too quick though!) and revive them plus I get some kills. The bonus?...Clusters can be stacked.
Proper credit must be given to Bonesickle (check out his Youtube videos, they’re excellent) for this. The red circle checkpoints in all the adventures have a timer on them…once any one player enters, the timer starts (approx 90 seconds) and once the timer runs out, all players will then appear in the circle EXCEPT on the second last checkpoint in Monastery (right before the end bosses). For that checkpoint, wherever you are on the map when the timer runs out is roughty where you’ll start the boss round (you won't be exactly in that spot so be careful and experiment).
Small jumps (where you still hold the gun in front of you) does not cancel reloading. Large jumps (where the gun goes to the side) cancels reload. Rolling also doesn't cancel reload.
Keep this in ind if you're not using RS and reload cancel is an actual problem (since you can get killed while reloading).