1st) Your post has me wondering just how the DO knew of Asmo's "treachery". The obvious is Lanfear, after her time w/ the Finn, presumably telling of her plan during her later interrogation/mindtrap at SG. Or do you think that Sammy, Grenny or Rhavin spilled the beans? Is there any hard evidence for any one person? I don't recall any.

2nd) The "You? No!" insta-death issue. I think it's entirely reasonable to assume that the OP was used, and perhaps even balefire. But this raises a question. The phrasing implies that after an initial shock of seeing whomever was there, Asmo then has a very brief moment of understanding regarding his imminent demise. If he was hit with BF, or really any killing weave (but BF being the best choice due to body removal and no need for cleanup..which seems likely) than don't we have to assume that Asmo was able to identify the weave as it was being formed? Assuming BF was used, I'm going to guess that it travels at the speed of light, and from a few feet away it doesn't seem plausible that Asmo would have time to get out any words as the BF was streaking towards him. This could probably be said with any killing weave from such a short distance.

Therefore, I think we may have to assume that Asmo read the weave, was able to gasp "No!" upon recognition, and was then near immediately killed. This would mean that it was saidin that was used to kill Asmo, and not saidar, no?