I've never understood how anyone can have trouble with Dota. The game is exceptionally straight forward. Read the description of the roles. Have a look at all the heroes. Play the extensive tutorial that teaches you ever phase of the game. Play against bots. Play against bots with people. Play a real game. Work out if it's best to 2 1 2, 3 1 1 or 0 1 3 + jungle. Communicate. Press buttons.
- 1 Hard Carry
1 Semi-Carry
1 Utility (varies depending on team makeups)
1 Support
1 Hard Support
Where do people have problems? Do they just dive into a game with no idea what anything is? You can't be having shit teams more than the enemy - rule of averages. The low skill brackets are also super easy to tear up; just pick Riki, SB, Husk or Drow, etc., and roll the enemy until it stops working. Welcome to mid tier bracket. Don't be an idiot. Understand the roles. Welcome to high tier bracket. Now it's challenging.
I think people must assume they can just pick any hero they like the look of and do anything they want. Rambo, one man army, "I do whatever I want" tactics don't work in multiplayer strategy games.