That poison works on a surprisingly large number of creatures as well. It pays to try it out. You can add it to ranged weapons too (for extra fun).
I've soloed an assassin most of the way through the game. I've also dual classed a solo assassin to a fighter at a very high level (after the first couple of HLA's), it was a lot of fun (Poison weapon + greater whirlwind!) once I got my thieving abilities back again.
The assassin dual classed to cleric is also a nice choice - the clerical strength and thac0 buffs plus a x7 backstab will dispose of pretty much anything.
Have you go the Rogue Rebalancing mod? It allows your assassin to dual wield and provides some nice extra thieving items:
http://www.gamesector.co.yu/avenger/
Edit - can't spell
[ 02-16-2007, 10:57 AM: Message edited by: Shard ]