Ruckus is vulnerable when he uses his ult. Remain out of his focus and shoot him down.

Yagorath's Caustic Spray deals damage in an area, and will hit your ult drones if she shoots at you. Try to stay out of range or out of sight so it's harder for her to target you.

As a massive hitbox without any shields or walls, Yagorath is an easy target. You can shoot her from a distance for essentially free ult charge.

Try to wait until after Terminus uses his ult to use yours on him. If you Dragon Punch before he ults, he'll just come back to life and you'll be at risk of being in the blast.