I feel just in place when I looked at this thread! I've been always jummping from setup to setup usiing the XRG for drifting, and I would always get the wrong line.
Consistency. I guess it would help you (me myself too =D), if you stayed with one setup, and hold the urge of trying to improve it. I don't know about you, but me, I can't improve setups, cause my driving just isn't consistent enough. I don't know if the car is understeering because I was pushing the car too much at T- blah blah blah, or if it was because I stiffened the rear spring.
I am in the same league as you. I've been drifting since last year with my joystick and currently a wheel just 4 -5 months ago. I've been taking this seriously just when I got back from camp, which was 4 days ago. When I get my S2s in a matter of days, (plus a week of processing), lets race together =D.
My BL1 times with the XFG is ~1:35+ 1:36- with the nominal setup I get online (sites, and fellow drivers). Remember, I am using a wheel. I am 100% sure you will beat my time, which sucks donkey balls, with like 30 minutes of practise.
BTW, get a Fanatec wheel. For the same price of a DFGT, you get something near the G25 level. (right?)
One tip, I'm sorry if I am repeating someone; I'm not read the previous posts, but try driving with the driving line ON -. Some people may think that is noob-ish, but I am doing that, where I can learn the lines a bit better. After a while of getting that second, I am going to turn it OFF. Try it. For the understeer, are you braking and steering at the same time. I could turn at ~80km/h in T1 for BL1, but I can't with brakes @ ~50-60km/h.