YacheChomp should live through ScarfStar's Ice Beam and OHKO with Earthquake or Outrage. Not sure about what the results for Cresselia and Suicune would be, but it still won't be pretty for them.
And there's another factor: Garchomp can viably run Choice Scarf itself, neutralizing those options. Crobat, however, doesn't really like running Choice Scarf. It means it won't have access to Roost, and taking 25% from SR every time it switches in, that isn't very good. With Choice Scarf, it also won't be hitting things too hard, not getting a boost from Specs, Band, LO, or Nasty Plot, and being locked into whatever move it chooses, allowing for switches more easily.
Finally, I'm not really getting how putting something with a Scarf at the lead is "overcentralizing." Several of those Pokemon, such as Rotom, Drifblim, and Froslass, work well as leads with a Scarf due to trick. They aren't hindering themselves just to counter Crobat, and work just as well facing other threats, so it would be more using a smart option for the lead that works both for Crobat and other things.
Other Pokemon I suggested, like Gallade and Honchkrow, have the Scarf as a very viable option for them to use. It can't really be called overcentralizing, since they also work well facing other things and aren't stretching themselves thin just for Crobat. They're just using a viable option, which also counters Crobat; hardly overcetralizing.
Plus, the Scarfers weren't the only things I mentioned. There was also Regirock, Steelix, and Electrode, which can handle it without being Scarfed.
There are plenty of options for dealing with Crobat, and none involve Pokemon having to stretch themselves thin just for countering it as was necessary for Garchomp, so I still don't see the need for it being BL.
