Are you certain this is the right log?
We found a couple of times where it spiked down to 26 FPS, and one spike to 24 FPS. But these look like isolated incidents. Other than those three instances, the log does not show any problem that can be classified as an FPS issue.
Does the problem happen with LazyRaider (vs. Enyo)?
The end of the log shows the WoWclient exiting. If this is an abnormal exit, you've probably got an interfering program. If so, these articles will walk you through the usual suspects: