Yeah but what If you don't have Gengar at the moment you need it when you got a Machamp as your Active while your Opponent's got Toxicroak G out reading to go out as the Active?
That's part of the problem though I seriously think a 3-2-4 Gengar SF line is very much needed to make sure you draw into Gengar when you need it the most. 3 Gengar doesn't cut it...
You're relying on speed early game to draw into both Machamp and Gengar and If you don't have both out by then tough luck.