It will run. But remember that you need at least 1 GB of RAM. Processor only matters to loading time. After the files are successfully loaded into RAM, it is RAM that plays the major role. The 1,66 Ghz speed is enough for the loading game and also random in-game loadings during the game.
Also remember that maybe you need one graphic card to perform more seamlessly. DotA uses very little graphic requirements. So even the cheapest graphic card will do well, such as nvidia 9300 GS.
I'm afraid installing a discrete GPU on the Atom platform is not possible, since the board doesn't provide any PCI-e 16x slot.
However, since the OP have had an experience with lower Intel GMA, then playing DOTA on the new Atom is an absolute yes!