There is now.  
It's not pretty, and there might be mistakes in there, I'll have to review it later.

You have to input the year, [otherwise the graph looks like a mess][1] (and I'm bad with graphs).  
And it probably needs a few less joins...  
But it's fast enough right now for ServerFault.

Fun little first thing I noticed, if you look at each year, the _0-100_ group used to be the minority, it has steadily grown to be the most active group on the site.  
Meanwhile the _10000+_ group has been slowly declining (all-be-it much slower).


  [1]: http://data.stackexchange.com/serverfault/query/382028/posts-per-rep-group?year=2015#graph