Nice image, like the capture of the whole lion including tip of tail! I agree with the others and personally would have cropped some of the foreground - it may be tack sharp but detracts from the lion.
I agree that increasing the ISO would be better. When ever required, I click at ISO 800. To me the ISO 800 of Mark IV is like the ISO 400, if not the ISO 200 of my backup 1D Mark II. I prefer to use a higher shutter speed with the Mark IV, than what I am used to with my 1D Mark II.