In the past few months, dotabuff has included a list of the top 100 players of each hero on each hero page. While the algorithm that dotabuff uses to calculate which players are the "best" probably isn't perfect, it does give a very good overview of the top players in the world on each hero. Given this, you can see that there are some differences for what it takes to be the best for different heroes.

Take a look at Lich for example, considered by many to be one of the lowest skill heroes in the game. Most of the top players have around 100-500 games on the hero with only a few having over 1k games.

Now take a look at what are generally considered higher skill cap/harder heroes like Meepo, Earth Spirit or Invoker. For each of these, as you'd expect, the average number of games played for the top players is significantly higher.

So my thought is if someone could do the math to find out the average games played on each hero for the players in the top 100 as a way to get a rough estimate of the difficulty/skillcap of the hero. Obviously htis is not perfect since the amount of games played goes into the dotabuff rating already, but I do think it may turn out to be an interesting way to rank heros difficulty in some slightly more objective way.

Anyway let me know if this makes sense to anyone/if anyone would be willing to do the actual legwork on this.

tl;dr: use the average number of games played for the top 100 players of each hero to get a rank of heroes by difficulty to master.