hardcore =/= skill, it's more a way to say that the player spend more time into the game....
naturally with more time invested skill come sooner or later to that type of player... since they can train more, they can get more skill.

then try to classify the skill of player based on them number of hours invested into the game is... funny, since some insane player are simply very good without spend countless hours into the game and same, some player can remain bad even if them spend countless hours into the game. worst, often they are not able to deal with different fight without a long training into the mechanic of this fight.