The problem with League's character designs is that they're generally just all too samey. It makes it hard ingame to tell who is what or even tell some heroes apart from each other.
DOTA has too many glowy eyed reverb demons, but they're all easy to tell apart from each other because they have totally different body shapes.
League falls into the trap of making everything a humanoid with realistic proportions. And as a result, while the champions look really cool on the splash screen, ingame they just sort of end up all looking the same.
I slapped this together quickly, it's silhouettes of five Dota heroes. While I doubt Dota players would struggle to name the top row at a first glance, I think you'll have a hard time naming each champion in the bottom row.