I own the A6 C8 quattro 40tdi for the past 3.5 years and I have the same problem. I'm not sure what car the people that say they dont have an issue are driving, but this is a known issue with this model. I even had an Audi engineer ride with me for half an hour to show me around the car and I showed him the 2-3secs delay from flooring the pedal to the car accelerating. He claimed it's a safety feature but obviously they messed up during design.
The first year or so I wanted to sell it and get something that won't get me into an accident. I'm now used to it and I'm waiting at roundabouts instead of risking it (I live in Milton Keynes so you can imagine). Another way is to learn to rev the car barely so it doesn't accelerate but enough for it to save you ~1sec at the roundabout.
