specifically with Gemini other than being a little over powered. Playing against over-powered heroes can actually be kinda fun.. More teamwork involved, suddenly everybody on your team stops being lazy and starts checking to make sure they don't duplicate auras, and victory is all that much more sweet. It's really not hard at all to cripple any particular hero on the other team in the normal game mode. Just ward enough and get your team to group up and go hunting. It's not complicated.
I can say that it simply isn't true.. When I started playing HoN there was about 20,000 people online at a time.. I remember last year when it went FTP there were over 60,000 people playing online at the same time... A couple weeks ago, for the first itme I saw over 115,000 people online playing at the same time.. I can't even guess how many will be playing after the buzz of HoN 3.0 dies down, but I'd bet it's over 130,000...
I'd say the major killer-feature that HoN has that DOTA2 doesn't is that HoN does a great job at putting culture into the game.. Remember the Nyan-Cat Courier? The Electrician Ghostbuster? The Michael Jackson taunt? The alt-avatars in HoN that speak other languages when you use them (French, Japanese, etc.).
I bought DOTA2, played it for a few weeks and wished I didn't.. Came back to HoN... I've spent a lot more money on HoN gold coins than I've spent on DOTA2 already and I still think it's worth it.