"Velasquez has the highest SLpM (Strikes Landed per Minute), landing 7.47 strikes on average per minute.
...
The article also notes that Cain is one of the most savage, ferocious, and violent fighter seen in MMA.
Looking on numbers alone, Cain seems to be a beast.
The way this number is calculated is the problem. Cain takes his opponent down, gets a dominant position and starts raining punches - huge volume often without much power. He landed 200+ punches on Kongo without finishing him and Rothwell didn't even try to block the punches at some moments because they were not harming him (although Big Ben was punished severely for his neglect of defense).
JDS' achievement - 5 or 6 punches per minute (that he lands standing) - is a much better feat in my book.
P.S. If we look on numbers without seeing where they come from Lesnar would be the best HW striker ever - his striking accuracy is 70%. And only further research will show all this great accuracy comes from GnP from dominant positions.