I play DotA 2 fairly frequently and I can tell you that DotA on a tablet is a pretty awful idea. You at the very least need 4 keys for all your skills, 2-4ish keys for your activatable items depending on what you have, a key to let you deny, a key to ping and a key for voice chat. It's obviously not as intensive as starcraft, but tapping a button to activate your skill and then trying to tap to aim it while you're running and chasing somebody would be terrible.
I'd love to see somebody try to play Invoker on a tablet. It's 4 key presses to change between his skills(possibly less if you manage your orbs well) and when you're high level, you can and should be changing every 5(or 2 if you have a certain item) seconds when you're fighting.
Unless they plan on only having Skeleton King available on this version. SK can be played with two fingers.