Try Paduk, grab the Gnasher and Lancer. Start with the 3rd room, kill the Drones in there, trigger the Juvies and leave. Go to the first room, rush in there and use the Ult+Gnasher to get rid of whatever is the biggest threat/usually the Mulcher/Stump. The damage should be enough to get your Ult back almost completely. Bring the Gnasher card since you don’t really need the Boltok.
Trigger the next Juvie spawn, run outside, Ult if needed and go to the 2nd room with the 2/3 Grenadiers and 2 Drones. Same procedure.
That’s why you need the Juvies 
