in 2014 ther were on average 4000 people online.
with 365days a year and 24 hours a day that makes for 35 millon hours of playing coh2.
now if you estimate the typical player to play the game for 10 hours that would mean that you had 3.5 millon people playing coh2 in 2014.
10 hours of coh2 may not seem much (i myself got 400) but i guess a lot of people got this game on sale, or as a gift and never even played it or just tested it for a couple of hours.
I would even say, 10 hours is quite a lot for an average player. Really a lot of steam games bought on sale are actually never played on average.
I like your approach, your analysis.
And in the end, it does not matter if the average is 10 or 5 or 20h ;-)