Hybrids with auto guns shouldn't be doing damage to terminator armor. I'm pretty sure this argument has been heard before.
Essentially, if matching in universe, the damage should be 0 or 0.001, which essentially makes the hybrid near useless as a resource in the game (from a developer perspective based purely on damage).
I have an idea how to fix this, in the way that the thorax swarm is used more as a debuff than a source of damage. When under fire from an auto-gun, the terminator should be affected by a debuff, movement speed slowed down, slight stumbling (affecting accuracy and recoil) and reduced melee attack speed. You can scale the level of debuff depending on how many auto-guns are shooting the terminator.
This would prevent the auto-gun from being as devastating in-game it currently is (not matching in the 40k universe) while still providing a threat in of itself by providing heavy weapon hybrids to do their job. For the sake of balancing with the debuff in mind, provide the heavy weapon hybrids with a slight buff to damage and fire rate, picking up the slack for the auto-guns lack of damage. Hybrid spawns could be tweaked so that they spawn in squads, 3 auto-gun to each heavy weapon.
Essentially, this would make the hybrids with the auto-gun effective while retaining the power level of terminator armor as represented in the 40k universe. Thanks for reading!