I have been using "C-x v H" binding for vc-region-history for a year and it has been super-convenient for me for the instances of "I wonder who made changes to this/these line(s) and when..". 

Also the "H" binding is still unused in vc-prefix-map and a good mnemonic for "history" too.

The attached patch binds vc-region-history to "H" in vc-prefix-map.

Thanks.