Is sorely needed. I'm not saying it has to be complex or prevent, but it needs to log. If people know they are being logged that is a very effective deterrence in itself.
Stat and secondary stat abberations need to be logged. This wont be too hard to code and get up and running.
GCD cheats on the other hand have me completely baffled and need to be shut down entirely. I'm no expert in programming, but I can't even begin to imagine how a local client tricks the server. In the very early days of warcraft such things were handled locally ((you got to me kidding me, right? LEL, but it's true)) since then everything is handled by the server. Maybe it has some sort of compensation for latency and if it does, that needs to be removed because people will find a way to abuse it. I've seen mages blink 4 times in 10 seconds and warriors charge 4 times in 15 seconds and hunters who somehow have roar of sacrifice up throughout the entire match.