If you suspect Mal'Damba has his ult ready, try to space yourself a bit from the rest of your team. Dread Serpent will knock you out of the air if you're flying, and its hitbox persists for a few seconds after it triggers.
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.