I didn't know TL2 is on origin. that's interesting. the game being distributed by them, personally on their site, doesn't matter. as for steam support, if game does not use CEG or Steamworks it's getting no kickback from Steam? Steam still provides a platform to communicate to userbase both converted and prospective, a platform for userbase to communicate with itself, metrics tracking, and patching and other maintenance functionality.
but I'm surprised to hear TL2 is on Origin. that does go against my exclusivity argument. I had no idea though and I've never seen them talk about it even once. still, that was in 2012, only a year after origin launched. that was the before times, when origin didn't even have a few supporters, and torchlight II's success on Steam.