In my opinion Hearthstone is really bad example of Esport. Everything you said is true and as a consequence
the outcome of a match could be that the better player easily can loose a match. (The single game can be easily lost due to RNG and torunaments are played usually to BO5) So there is a big chance that fairly good player can beat the top level player just because of luck. That shouldn't be the case in my opinion and it's really bad example of e-sport. hearthstone is E-sport just beacuse Blizzard thinks it's a great idea and game isn't Esport ready, not even in 10%. The outcome of a match should depend on a player skill not RNG (to achive this in hearthstone you have to play a match to something like BO25)

However I don't think that RNG is a big problem in COH2. best players have a 80-90% winrate so they can manage to deal with unlucky situations. (in hearthstone bes player have 59% win in torunament games)