It's been made clear that the reason he can't be brought back was intrinsic to the WAY he was killed as well as the WHERE. Therefore it's completely relevant to who done it.

Given RJs statements about the way and place of Asmo's death, and the fact that all the pieces were there for us by LoC I find it impossible to come up with Slayer, with poison in TAR as the solution. Not to mention that the TP (or lack thereof) is the reason Asmo can't be retrieved.

1. We don't have any proof that Asmo's soul couldn't be reclaimed due to death in TAR

2. Even if we did have this proof AND the TP somehow counteracts it we have no way of knowing that the TP and the "black cables" were different things

3. We still don't have any clue if Asmodean would have known Slayer

4. Doesn't explain how RJ called Asmo's death as "one of opportunity" ... if Slayer did kill him you can't call it opportunistic since Slayer would have stalked him and killed him on his own terms ... that's what Assassins do!

Compare to Graendal as a suspect:

1. She's linked to BF almost from her first appearance ... Rahvin thinks to himself that he will flee if Lanfear and Graendal get into a duel and BF comes out.

2. She's openly threatened to kill other FS a number of times

3. She's got reasons to go to Caemlyn after Rahvin's death and the Pantry is an excellent place to find future spies as DomA described above.

4. She doesn't know Asmo is shielded so a quick BF death would be logical in a moment of surprise. As opposed to the Moghedien/Cyndane scene she when she was far more prepared.

5. We know for fact that Asmo would recognize her.