This is a silly comment. A cursory search of "League of Legends Bugs" yields similar results, lots of bugs. In fact, the Mac Client was rendered completely unplayable less than a month ago, which may have been fixed by now. Valve employ people that build automated testing (which very well may have built a system used by Dota 2 devs), so I think your last statement could be incorrect, but either way it is speculation, unless you have a source for that.