SM main here. I have been getting hit by large groups of shadow spectres quite a bit recently. Setting aside the fact that I probably screwed up by letting such a thing be constructed in the first place, what are their vulnerabilities? They should be vulnerable to large groups of melee infantry, but it's too easy for them to hit and fade. I was jumping in ASMs but not able to really get them to stay long enough to die.
I'm thinking perhaps the strategy is to just attack, and force them to engage rather than harass.