Valve has been pretty outspoken about their thoughts on the rise of mobile gaming, especially regarding mobile gaming on tablets, and how it will be a major force in the industry in the near future. It is then no surprise to find out that Valve wants to bring their popular MOBA game DOTA 2 to tablets and, in fact, already have a working version of the game on an iPad.
Unfortunately the result of the prototype version wasn't that great but Valve is keeping their sites on bringing the game to tablets in the future once the hardware gets a bit more powerful.
We were working on getting Dota 2 running on some tablets. That ended up being kind of a disappointment. But the good news is that tablets are getting faster very quickly, so I think we'll get the kind of performance we want and other game developers want in the near future. - Valve's main man, Gabe Newell
So for right now we will have to rely on Heroes of Order & Chaos for our mobile MOBA fix. Of course if you absolutely have to play DOTA 2 or similar games on your tablet right now, you could always try streaming it from your PC to your tablet using Splashtop Remote Desktop.