main problem of dota2 (as any other team-oriented mmo) is not the language barrier, but those braindead ones who do not care in the slightest what is going on, what's the setup, or what team needs.
simple as that.
Which, is no surprise.
Its internet, after all.
We all are Rambos on internet, each one of us has an ego the size of a tank.
that's the main problem.