There is a good reason why no one has written one yet...
After spending a few hours getting the game downloaded, I loaded it up, and noticed that it was QUITE laggy. The source? Their particle effects are sloppy. Yes. They really are. They are so sloppy that I had to turn them off just to have a normal framerate. I had everything else cranked all the way down... But once I turned on particles, BAM, lag. Quite silly to think about considering I can crank games like Team Fortress 2 up to max possible settings and not lag. Portal 2, nearly, but aside the point.
It all came down to presentation for this game... And it does that horribly.
http://store.steampowered.com/app/90530/ The website is shiny.
Bad-
-> The particles are very sloppy.
-> Not technically free.
-> Yet another DotA clone.
-> League of Legends has a bigger community base, for good reason, Rise of Immortals sucks.
Final thoughts? If you want to play a free game of this style, steer away and just go play League of Legends. I think even Defense of the Agents is free, so why not play the original instead of clones?
Steam, please get rid of this piece of crap.