Someone sent the Trollocs to Ebou Dar. I think there is no Waygate nearby, so it seems that they were brought there in another way. Maybe a True Power Gateway would work? Apparently only Moridin has access to the Shadowspawn armies now, and he forbade the other Forsaken to use them (like "Sammael" did in KoD). Normally it wouldn't make sense to let Shadowspawn attack at Seanchan territory, because it might convince them more to ally with Rand against the Shadow. But maybe the Shadow risked it to achieve a great victory. The actual target of the Trollocs might have been all the gathered Tinkers at Ebou Dar. We already saw - yet unexplained - that someone slaughtered a Tinker band in LoC (there was also a message to tell this the Dragon Reborn, which never happened, IIRC). Tinkers were also slaughtered in TSR during the Two Rivers plot. Maybe by killing the only really "good" and peaceful people left (the Amayar are already gone) the Shadow would achieve a mayor victory, especially if the Tinkers are e.g. needed to counter the spoilage after they find the Songs.

I think the Shadow will again try to destroy the Tinkers in ToM or AMoL (maybe the Super Darkhounds Pack's next purpose?), while the Lightside has to prevent it at any cost.