i'm in shock. You have the EXACT same wheel as me? Same game, definatly not A DRIVER ISSUE (pc hardware driver, not operator) , you definatly went into the controller wizard + advanced setup. I belive you, just odd that it works fine for me and my wheel and not your wheel.
My friend John : "dude im playing with a controller where I spliced the wires twisted them together and used some elec tape, and i have a ps2 to usb converter" he got a 38.4 btw
If the steering is that bad for you. then ya it won't be realistic or fun, and you won't have a chance to beat my 38.9xxx
You know i Used to have the same feelings about toca 2, horrible input , horrible dead zone, then i found something in the controller setup that changed everything (EVERYTHING) night and day difference, but i don't recall what.

you must be running into what ever my previous issue was though.
sounds to me like your wheel works fine for GT Legands , and is acting drastically , drasticaly different on GT legends then Toca 3 (mine feels / works very similar on both comparing full driving assits in GT to Toca3 "sim" or novice to 1 below Pro and toca3 "full sim" )
*sarcasm* with only 1 person able to play the game happily i see this taking off bigger then the GT4 thread ...