YouTube compression has destroyed this video. I downloaded it @ full HD 1080p and it was just 82MB for a 5 min file, which normally would be about 1GB in-camera before editing.
The softness (even @ f5.6) was quite noticeable, plus the aliasing is horrendous - look at the black rubber zoom + AF rings on the lenses; they are positively dancing! I think it has a lot to do with YouTube compression and downsizing of the bitrate (to reduce file size).
Finally, I did apply a few effects in Adobe Premiere Pro CS6, like Anti-aliasing (had no effect??), some color correction (boosting the backs a couple of percent looks a lot better), plus Sharpening (50%) really improved it. However, the high compression (just look at the pix-elation and block patterns in both the whites and the blacks, as well as along the edge of your hand) makes it look like 240p and not 1080p! Btw I watched this a couple of times on YouTube at 1080P HD on both my HD monitors (one 40" and the other 25") and it just doesn't appear to be proper HD. It is a shame as you obviously went to some effort to capture and edit it. Even your titles and banners look soft that has to be YouTube's fault -> I bet the lettering of your text/titles looked great on your original edit.
How much of these issues are due to the high-ISO used is not possible to determine due to the nature of the destructive YouTube file processing.