Warped rotors are felt as a (usually) noiseless rhythmic pulsation, sometimes vibrating the entire vehicle. It is especially apparent when when braking at about 50% pressure - i.e., on a long incline.
Hard braking sometimes masks warped rotors since the pulsation is caused because the brake pads grab the higher spots (peaks) and not the lower spots (valleys). Under full braking, the pressure on the pads is so great the pads "ride" the peaks and the valleys and the brakes feel ok.
If you only feel the pulsation in emergency braking and there is an audible very-fast-pulsating-sound as you come to a stop, that is probably your ABS - working properly. The vibration is also limited to just the brake pedal.
Of course, if you hear a grinding or growling sound when coming to a stop, you might also have worn pads altogether. This is not good news as your rotors might need to be resurfaced or replaced. The good news is that total brake pad wear is rare since MBs have a brake pad indicator light on the dash, as you know.
Hope this helps.