I used to think this too. Eventually I learned that being down 9 kills to 3 (for example) is meaningless in itself. It's only relevant if youre down because your team is much less skilled (and the ratio will always be 9:3) or if you concede (and/or) throw the game beCAUSE you're down 9 to 3. I've been part of 15 kill deficits and come back. I've also been down 6 or 7 towers and come back. If you're on a team that wants to win rather than improve their precious K:DR, its not that unusual to see big turnarounds.
Easily the biggest problem with snowballing in HoN is that people give up instead of playing smarter. In the 1000+ games Ive played, I've noticed that its a problem with the community, not an game mechanic flaw. The community is generally shit.
On occasion there are still games where I honestly don't believe it's even possible to win, but a higher rated carry will ask us not to pass the concede vote, and eventually we pull ahead.
On the topic of DotA2, I love the looks of the graphics. Its incredible. I like the visuals in HoN but in direct comparison, HoN looks way too busy. And the color pallet in DotA 2 is phenomenally better than LoL. I'm pretty stoked to see gameplay footage.