I would disagree that he necessarily suffers against weather teams. Heatran fits well on bulky teams that should be running Trick Room in this meta. The idea isn't that you will use Trick Room in every match, but rather to use it to screw with opposing speed control. You see weather sweepers? Turn on Trick Room! Opponent sets Trick Room? Turn it off! Heatran is sitting comfortably in the middle between stuff that's fast and stuff that's slow, meaning that if you get the Trick Room setting you want it's actually in a pretty favorable position to be useful against both archetypes. Of course you still need to win that favorable Lockdown, but that's a central battle in this metagame and again Heatran helps there by checking or countering many common leads.Heatran: A-
Great lead as it has Taunt, Stealth Rock and Sunny Day. Suffers against Rain, Sandstorm and to a lesser extent Trick Room, but on Sun teams it's great for its ability to check opposing Fire types.
Oh, and I've got a Grassy Terrain team with Heatran on it that needs testing. I guess I've given away that I've got a Trick Room setter, but I don't think that should be too surprising in this meta anyways. I'll try to drop by the OM room tonight and tomorrow over lunch break (Pacific time here). Anyone who wants to have a lockdown match (my nickname on Showdown is Darvin3) give me a shout.