There have been posts on this forum and on the feedback page about how Scyllas are too easy to incapacitate and kill with certain combinations of abilities and weapons, and how preparing fire on Scylla Blaster Cannons should be removed so that Scyllas have a lot more opportunities to attack with them. But there is one more thing that I think needs to be considered so that Scyllas are rebalanced to improve their offensive and defensive capabilities to the point of making Scyllas a proper challenge to fight, without making them too difficult and frustrating in the process.
I think the Scylla’s Smasher Arms should do Area-of-Effect damage, instead of just doing damage against single targets. If the damage and shred that they do is changed to be slightly lower than what it is now, but includes a wide Area-of-Effect in its statline, that could make Smasher Arm Scyllas much better at fighting a whole team of operatives at once, without them one-hit-killing full-health operatives in just one turn. It would also do a lot to prevent players from just blocking and tar-pitting Scyllas with Spider Drones, if Scyllas can take out all nearby spider drones with just a single Smasher Arms attack instead of having to fight them one at a time. The attack animation for the Smasher Arms might have to change to be more of a sweeping motion though, to account for becoming an Area-of-Effect attack. How big the Area-of-Effect should be would have to be considered too.
A lot of different things would need to be rebalanced so that Scyllas become tense and formidable enemies to fight against without making them too difficult. Personally, I want a fight against any Scylla to be like a memorable, suspenseful, back-and-forth struggle over multiple turns, like a genuine boss fight.
Rebalancing Scylla Smasher Arms to do Area-of-Effect damage, I think, could be another piece among many others to help complete the Phoenix Point gameplay balancing puzzle.