Hey Dantastic...
Sorry, but the wobbly crank pulley on my '86 Jetta made the car vibrate at idle, only when the compressor clutched in. At driving speed the vibration was at a much higher frequency, and it didn't shake. It's all about what frequency resonates the engine mounts.

On that pulley it was the rubber insert getting old & loose. You could see the pulley run pretty straight, until the AC clutched in. Then you could see it wobble a little, but I was surprised how little wobbling it took to shake the engine.

But, it sure can't hurt to check the engine mounts anyway...