I think if you can get Swampert burned, Snorlax should have no problem with it. Then, were it to Rest everything off, I'd explode to take care of it. Swampert isn't going to come in on Gengar to take it 1v1 and Gengar doesn't want to stay in, Giga Drain and risk a OHKO due to Hydro Pump.
I'm...