It seems possible to have, at last, user statistics for each article in its history page. Two pies, one showing bytes/characters per editor and one showing edits per editor would be useful. Not ideal, though, as reverts of vandalism would count bytes, too.
Article contributors pie
Right, I think vandalisms, especially page blanking, would totally skew statistics, making it somewhat useless.
Vandalism/Revert pairs could be excluded.
It's not that simple. Sometimes there is multiple edits that all get reverted, sometimes reverts are not marked as such. Plus it is not very straightforward to do this from Vega, and Lua has to be used.