Is this the first time you've played Dolphin on this computer? Dolphin needs to generate shaders for each game, but once it's done that once, it caches the shaders for later reuse. The initial generation of shaders is known to cause drops and dips in FPS. Have you tried extended play sessions? Lastly, what about the latest development builds (4.0.2. is old and slow) have you played on those yet?
If you, for example, manage to play 10-15 minutes and still get those speeds, can you clarify what the FPS range is? It's very hard to tell if this is a serious issue (like getting 10 FPS) or if it's something relatively minor. Be sure to post your Dolphin settings (as screenshots) too if you continue getting low speeds. FYI, I am not nearly OC'ed as high as you, and my GPU is fairly weaker, so you shouldn't be getting any issues of this sort (normally I mean, obviously it's happening to you now :p)
If you, for example, manage to play 10-15 minutes and still get those speeds, can you clarify what the FPS range is? It's very hard to tell if this is a serious issue (like getting 10 FPS) or if it's something relatively minor. Be sure to post your Dolphin settings (as screenshots) too if you continue getting low speeds. FYI, I am not nearly OC'ed as high as you, and my GPU is fairly weaker, so you shouldn't be getting any issues of this sort (normally I mean, obviously it's happening to you now :p)