It was the common sense thing from a consumers perspective to make DotA 2 into a product. It's just funny that Blizzard didn't manage to be the ones to do it. I remember that at the time when DotA was a popular Warcraft Mod me and my friends were often talking about how Blizzard should do what Valve did with Counter Strike and hire the modders. In the end Valve made that obvious move themselves, but maybe it's their flat structure that makes it possible for them to absorb external talent that way more easily.