A lot of BW2 threats, like Garchomp, can almost guarantee taking out one member of a stall team if they go all-out offensive. Haxorus, Thund-T, and Terrakion are actually better at doing this. They're all really good at beating you if you give them free turns, and if they run a specialized set, but in Garchomp's case Yache SD is most universally useful which a tough stall can deal with rather easily on its own. It'll have to eat a Toxic / Leech Seed / Ice move / WoW trying to set up unless they make a risky prediction to double it in on Heatran or something, in which case you can still easily check with stuff like Glisc / Quag or Whirlwind with Skarm if you need to. Tangrowth isn't even 2HKOed at +2 if it doesn't have Outrage so you can seed it and then go to Quag / Skarm or start HP Iceing. If it tries to lead against Heatran it's not going to do lasting damage anyway if you have walls.
Life Orb sets will mostly run through stall so if you're worried someone would run that (it's only needed for wallbreaking and is less useful against offense by far, which is way more common) you can just hold off on sending out Tran for a bit and begin your game plan with things that can prevent Chomp from setting up, until you have T spikes or have worn it down. It might be a longer game but you're running a stall team. You might have to lose one pokemon to take out another but it is a pokemon game.
If you're going to argue that a properly played stall team loses to Chomp you have to at least mention the things like SD Haxorus / NP Thund-T that it really does have no hope against.