you sure that it was not due to ABS?

If you press the brake pedal hard enough for quick stop, you may activate the ABS in which case you'll feel vibration. That's normal. Otherwise, normal braking condition shouldn't give you that. However, if you have warped brake disc, then it could cause the issue. But it's a rather new car based on your description. So it's either ABS or really poor quality build. If it's latter, don't accept dealer's so call "normal" answer. Ask them to change brake disc.