Here is the thing. HoN was made to be like DOTA, but without the limitations of the Warcraft III engine plus extra features like matchmaking.

DOTA2 is also trying to do the same thing, but is being made by Valve and have Steam support.

LoL at least have their casual approach and playerbase, they may stick around. But HoN and DOTA2 are basically trying to be the same game, and there is not much room around for that many DOTA clones.