These are pretty good at map clearing with profane bloom. The jewels are quite expensive, if you don't have currency to buy them, I would not recommend going occultist just for explosions as you'll lose a lot of dmg.

Overall these spectres are in the middle of melee minion rankings (not great, not terrible).

My PoB https://pobb.in/zlUZVQ5cVMyg

https://poedb.tw/us/Syndicate_Silencer#SyndicateSilencerBetrayalSecretPoliceChampion

Get them from syndicate hideouts, be quick as corpse disappears fast.