I feel your pain! Mine was shot between ISO 1600-3200. At first I thought it was useless but Avidemux did a great job. I got pretty decent results with the compositor too -though admittedly not as good. If you downscale to a lower resolution (say HD) its not perfect but fairly close.
Btw, I got my new f1.8 lens and I’ve been stunned. Combined with Magic Lantern, I’m able to produce almost noiseless shots even at ISO 400! Not to mention the fact that shooting with an ISO 600 in dim light practically feels like shooting at ISO 100 in daylight, morning/afternoon. Just wow. Guess I will become a believer!