I agree about the squirming under braking, but at 70-100 mine are fine, they're alot better than the RS2's I had, first hot day they ended up coating the sides of the car in rubber, the RS3's seem a lot better plus they grip from cold quite well on my 172, but then i've had tyres people with other cars said were great and on mine they were garbage, I guess tyre performance differs depending on what car you have, on Clio's they're fine, on a Golf R they're obviously sh*t going by your experience.
Also I usually have 30psi on the front and 33psi on the back but the RS3's looked flat and felt soft as liquorice allsorts, so i've started having 40psi all round and they're alot better, try sticking in 7-10 psi more on your Golf and see how you get on.