Obviously it feels that slow because you are used to a different sensitivity. The opposite is true for people that are used to lower sensitivity. I started playing on default 6 sens but switched to 4 after a while, then to 3, played on 2 for about a month, then switched back to 3 which I don't switch anymore. It is a little bit too slow for effective shotgunning imo but it is good for my primary aim and is good enough for sniping