Garchomp just rang. Asked if you'd allow him back into OU despite being the best at what he does.
It was practically impossible from stopping Garchomp from setting up a sweep and taking out at least one or two of your Pokes.
Crobat, on the other hand, doesn't really compare to it. It's 90/70 offenses are good, but not too great or game-breaking. It's support options are mostly just temporary, like Sunny Day and Rain Dance, are predictable and can be dealt with (Taunt), or terribly inaccurate (Hypnosis). It's fairly bulky, but not terribly so. Throw a Scarf on something with at least 71 Base speed (Honchkrow and up), give it a super-effective move, and it will be dealt with.
Speaking of Scarfkrow, it's a pretty good counter for Crobat and has been my primary answer to it. Outspeeds, is immune to Hypnosis, and HP Rock takes a hefty chunck out of it. It can also go for a more supportive role and screw it over with Thunder Wave.
Then there are the Pokemon that Lemmiwinks mentioned; ScarfBlim (which can screw it over with Trick) and Steelix, which can wall any Crobat not carrying Heat Wave.
Then there's other Pokemon. ScarfLass can screw it over with Destiny Bond, Thunder Wave, or Ice Beam. Electrode outspeeds and can also Thunder Wave Crobat, taking away its greatest selling point (its speed). ScarfVoir/ScarfLade can hit it with Physcic/Psycho Cut. ScarfGatr can get it with Ice Punch, as can Scarf Floatzel. ScarfTauros gets it with Zen Headbutt. ScarfCroak, Stone Edge and ScarfTom, Thunderbolt/Thunder Wave/Trick. Regirock, while being unable to outspeed, walls it and hits it with Stone Edge.
There really are no lack of ways of dealing with Crobat, so I don't get the calls for it to be BL. Yes, you can predict it and switch it out of those things, but your opponent can play the prediction game too, and get those things in on it, where they still counter it.