Thanks for the informative (and accurate!) replies.
Even without triggering Dual Wield, Lethal Strike DOES rock. As for DW's effectiveness, I agree it's not as good as it could be (due to the randomness)--I just love watching the animations though. Hah, and it's entertaining to hear the explosion of 3 or so hits at once, then see all the enemies rag-doll launch away from you!
(Actually the only skill you need as an Assassin is Flash Powder. I don't see how the class could be possible without it.)