Seems like Luc can channel. When Perrin acts to save the Whitecloaks, one of the Ashaman senses a weak channeler channeling nearby. Presumably, the channeler is using the OP to transport Trollocs through a Portal Stone.

We know that Graendal was using Isam/Luc as a "tool", loaned to her by Moridin. I think it is a fair inference that Luc was the channeler, and that he's relatively weak.

Perhaps this explains, in part, his disappearance? While being told by Gitara Miroso that your destiny lies in the Blight might be good enough for some, if he was beginning to channel and feared he would go mad, a kamakaze-Aiel-like trip to the Blight would make even more sense. (By the way, my initial take was that some of our kamakaze-OP-wielding Aielmen are now the red-veiled Aiel we see at the end of ToM.)