Here is what I said in the comments that shows how great he was:
He led the NL in WAR (Wins above replacement) for pitchers 4 times, plus a 2nd, a 4th and a 5th and is 47th all-time.
All of his WAR comes from age 31 on.
He has the highest relative strikeouts per 9 IP ever for pitchers with 2000+ IP (table below).
He also has the highest relative strikeout-to-walk ratio ever (table below).
He led the NL in strikeout-to-walk ratio 8 straight years (I think only Mathewson matches that).
He allowed about 20% fewer HRs than average.
He led the league in ERA+ 3 times (that is ERA adjusted for park effects).
He led 8 times in strikeouts per 9 IP.
He led the league in fewest hits per 9 IP 4 times.
6 top 5 finishes in walks per 9 IP.
Led NL in FIP ERA five times (that is an estimated ERA based on only walks, strikeouts and HRs).
This last one is impressive because I don't think his main park, Ebbetts Field, from 1922-32, the bulk of his career, helped him. I found the average park factor for HRs in those years using Seamheads.com Ballparks Database. I used the 3-year averages for each of those years and found a weighted based on IP. Here is how they broke down:
All batters: 102.5
If I had used the 1-year factors, things came out almost the same. The 102.5 means that his park allowed 2.5% more HRs than average. Now it favored him against RHB but he was a righty, so the 116.3 against LHB stands out.
The table below shows the top 10 pitchers in relative strikeout rates. The 213 for Vance means his rate was 2.13 times the league average (which gets multiplied times 100, 6.20/2.91 = 2.13)
|8||Van Lingle Mungo||160||5.30||3.30|
The table below shows the top 10 pitchers in relative strikeout-to-walk ratio.