I think telepathy, like teleportation, are too obvious plot devices.
It all sounds like an insider, with a motive, from old JLA continuity. The Red Tornado / T.O. Morrow team fits the bill. I can't think of anything else, other than a hero turned bad, but in which case, what is the motivation? People have been talking about Martin Stein - why would he want to kill the JLA's wives and relatives?
It could also be Starro, I guess. That would explain the different methods of attack, and the lack of information from the villains. Starro uses their skills, and then wipes their minds. But that doesn't strike me as particualrly clever.
