Agreed (about Verin). I'm thinking more about how Semirhage's (?) Trollocs fought against the Trollocs invading the Stone in TSR. Moridin has also helped out Rand before. It's not impossible that someone on the Shadow side wanted to do something similar for reasons we don't fully know about yet.

I just don't think that it was a concerted attempt to kill Tylee, though she's certainly an attractive target (and one who Demandred at least would have known about via Masema). It might point to a Trolloc army being formed somewhere WITHIN Randland (eg Murandy, for all those who subscribe to the King Roedrandred theory).