That an Eelfinn assassin killed Asmo, but in the end there are too many assumptions and problems, IMO, especially:
Did Lanfear actually got any wishes? Was one of these wishes really to kill Asmo? Did the Eelfinn have a Gateway ter'angreal and a balefire ter'angreal (the latter such weak, though, that the DO could theoretically transmigrate Asmo) to achieve the murder?

RJ said in an interview "that if occasion permits in the last book and it seems appropriate, the character doing the deed will probably think to themselves about killing Asmodean. However he gave no guarantee. But he did say he will reveal Asmodean's killer if he doesn't in the book before the paperback of book 12 comes out."

I think people would have lynched RJ, if he revealed in the last book in the first PoV of "Fred the Eelfinn killer" that he was Asmo's murderer. That's in no way obvious. But maybe one could eventually ask BS, if Asmo's killer was seen in the books before Asmo was killed, since RJ said, after all, that it is intuitively obvious. This could e.g. most likely rule out a special Finn, the gholam, Moridin, Mesaana and Taim.

Besides that, there seems to be a time issue, Lanfear already was in Finnland for many hours, why was Asmo killed much later?

Anyway, I think we file this Finn theory under "loony Asmo-theories", and if it turns out that you were nonetheless right, I give you a beer!