The Mac WoW client has a recorder built in. It's not necessary to use Fraps for Mac.
It can be done in VirtualDub, but like I said in the guide, if you've cut any parts it likes to skip the audio file around, so it's better to do it in two phases if you want to do audio within VirtualDub.
Overall I like it. Nice titles especially. The black bars on the side bug me though, but that's simply a matter of your resolution.
Might want to mess around with your aspect ratio and resolutions a bit to bump it all the way to 1080P, but it's not a big deal if you don't feel like it's worth the hassle.