Well I tried playing DOTA once, the difficulty definitely comes from a different mechanic than the one in league. It was awkward as fuck to play, using a skill costs half my mana bar, and so many items were op as fuck. The difficulty comes from the game itself, whereas in league, the difficulty comes from other people's mechanical skill. I doubt we'll be seeing mlg 420 faker zed outplays in dota, cos there aren't any to be made, that kinda stuff only happens in league. An outplay in dota probably consists of buying an op item to counter their not as op item, or not using more than 1 skill so you don't run out of mana.
Tl;dr lol has more mechanics to do with aiming / reflexes / prediction