Use your Power Siphon to absorb his shots, and get behind a wall to recharge it. If you're running Decimation, you can shred half of his health down at max charge for your flanks/damages to finish him off, or at least force him to retreat and heal.

When dealing with Strix, it is paramount that you get the jump on him. Try to aim your Net Shot during Heroic Leap, and with Ensnare he'll go down fast. Strix has the lowest walk speed in the game, so even in his stealth he won't be moving too much.

Void Grip makes him an easy target for your team, although it also leaves you vulnerable to his Grumpy Bomb. Void Grip him when you can quickly escape behind a wall so he or his allies don't punish your open defenses.

If Grohk uses Spirit's Domain, his lightning doesn't hit through allies, but his Shock Pulse does. He may try to stay in the front if they group to get some damage in, so use that opportunity to burst him down.