I'm very confident that Torchlight II could of beat Diablo 3 game play wise and content wise if only they didn't let it run wild like open battle net.
Has anyone tried Torch Light II? You join a game and you have all the gold in the world / duped items / stupid modded weapons. Why couldn't they have kept these modded games and regular games separate Diablo 2 had two different character rosters, open battle net, and ladder / non ladder. Did this bother anyone else? IT completely ruined this games chance to flourish with trading/bartering some sort of item based economy... a reason to farm items... etc etc.
Everybody knew the pros and cons from the beginning. Torchlight 2 has unrestricted offline play and mods, Diablo 3 has a secure persistent economy. I recall a lot of people heaping praise on TL2 for making that choice.
I don't think Runic even thought it would kill D3. I'm sure they're more than happy with their small company, supportive community, and 1 million sales. No need to go after the big guys, anyway. So long as they can afford to make another game, I'm sure they're content.
People take too much stock in which game is "winning".