According to the wiki it is considered as a “Viral Weapon”, only Priests are proficient (Proficiency with viral weapons) and there is no personal perk (as there is none for crossbows).
Only if the proficiency is given, so you have to cross class to Priest to get Quick Aim and Extreme Focus (the cheap overwatch) work with the Subjugator, this is the only way.
Scylla is my main monster problem. It is just too tough to take down with bullets. Paralyze is great, but it takes too long to do that while needing to take out the other monsters. PANIC came to mind.
Though Scylla is huge and can be hit from afar, Priests are too slow to get into position to shoot. I found a better alternative: Biochemist + Shardgun! Dash into position, shoot, dash out. Two shots and Scylla is out!
If you shred the armour they last <2 rounds of focus fire. They usually start out out of the way so I try to clear up most adds before waking them up then shred the armour then they melt. Usually a heavy will shout at them once or twice to mitigate their nasty attacks. Really paralysing them takes longer, partly because not everyone will be able to contribute. Biochemist plus Shotgun or PDW is good to control them though for sure.
Also much harder with fewer guys.