My defiler is 34 and I have played around with 1hp, 1hb, 2hb and 2hp. Not a single darn one of em has made me do any damage worth mentioning. I don't have a parser so this info is a bit soft however the most damage I have done in a single attack is about 25. That was with a big 2hb staff that drops in Varsoons. (really nice item btw). Now say I land that 25dmg every time I swing which is like once every 2.5 seconds. That gives me a dps of 10. Not even worth it.
As far as weapons go find the best combination of 1h + offhand item, or 2h you can with +Wis on it. For DPS purposes this will allow you to stack more DoTs on or nuke a little more. The last thing you should look at as a defiler when looking for weapons is the dmg/delay on them. It's pretty much meaningless to us.