If you're using a dagger mainhand, look into replacing it ASAP. For the OP, I'd recommend getting a Runic Hammer crafted or holding out for a Decapitator off Prince.
I'd still call the offhand weapon-speed question open for debate, however. I haven't seen any reliable evidence for slow blue offhands being better than purple daggers.
If you read through the "The Change to Windfury and You" thread (
The Change to Windfury and You! (does not apply to warriors) ), you'll find a lot of discussion about midway through the thread about how Windfury isn't working exactly as expected. Mainhand procs can proc offhand windfury. Offhand procs can proc mainhand windfury. That discussion gets abandoned pretty quickly, because, well, we don't know what causes that so nobody has anything further to say about it. Which is unfortunate, because the logic behind slow offhands being substantially better hinges on the idea that offhand procs always proc offhand windfury, which is demonstrably not true.
The thread then moves on to slower weapons being better, based on:
(1) Disquette's scripted model, which, while pretty awesome, assumes that a proc off one hand always triggers damage from that same hand. It also, by Disquette's own admission, under-reports white damage.
(2) Some really horrid live testing done using lv10 gray vendor items, without enough test time to gather any statistically significant data. This test was posted on the official WoW forums, and I suspect it was as much a grab for the CMs' attention as anything else.
I'm not aware of any reliable live test which shows slow weapons being so much better than fast weapons that downgrading a Malchazeen or Emerald Ripper to a High Warlord's Cleaver or Boggspine Knuckles would increase your DPS.
Furthermore, when I tested it, the typical explanation for slow offhand > fast offhand (offhand WF procs will "lock out" mainhand procs and reduce your MH proc rate) didn't hold up. I logged the number of mainhand vs offhand procs using Black Planar Edge (slow mainhand) and Malchazeen (fast offhand) and didn't see any fewer mainhand procs than expected. My ratio of white mainhand swings : white offhand swings is 2:3. My ratio of mainhand to offhand windfury procs was the same. (Test results are on page 11, down at the bottom.)
My personal opinion on enh weapon itemization: get a slow mainhand, for sure. For your offhand, if you have a choice between two weapons with similar DPS, take the slower one. However, if you get access to a fast offhand that's a tier above your current offhand, go ahead and take it.