Yeah, I almost didn't do it as I suck in the X cars but I did it after doing about 8 or 9 of the Goodwood ones in a row so I was used to the course. Having it at -2 does mean that you have to really push the stick left and right quite hard but it is doable....if you are finding that it doesn't turn quick enough for you then either increase the sensitivity slightly or just start turning into the corner slightly earlier. It's easy for me to sit here having done it and say it just takes practice but it does...my first couple of runs at high speed and I couldn't get past turn 1..once I cleared that, I was able to progress.
As I said, just focus on one corner at a time, work out your speed through it, keep repeating it and then move on to the next corner. I would definitely recommend looking at videos of it in the video section...I used them as a guide to know what speeds I needed through the corners and then just aimed slightly lower. Overall, the run doesn't need to be perfect...after the left hander at the bottom of the hill I had 3/4 of the car on the grass but managed to coax it back on track...just be as smooth as you can
Edit: Try this video..it's someone using a DS3 to show you how unperfect it needs to be. I would suggest focusing on the corner speeds:
https://www.gtplanet.net/forum/threads/goodwood-festival-of-speed-x2010-dualshock-3-gold.294122/