So I'm past the point in-game at which others said their FFB was suddenly fixed and mine still isn't. I tried other games to check it wasn't a hardware issue: On Dirt Rally 2, where you'd expect to feel the road, it's perfect. Also that game puts the wheel options of Gran Turismo to shame, but that's a side note. I tried GT Sport, which I had never tried on wheel, and it seems GT games give very little FFB for road feel in general compared to all other games I've played in this category (AC, ACC, F7, F1). That said, I could feel grip to some degree in GTS and definitely curbs, but still nothing in GT7. It definitely seems like a bug.
Also, I understand that RWD cars in this game are harder to control, but my earlier statement still holds up. Without road-feel, you find out too late that the car has broken traction to have time to correct it, it's a compound issue essentially with how cars handle in this game.
PS: I did want to mention that I can actually feel the paintwork/bumps on the road on Tokyo Expressway, very heavily in fact, like I'd expect to on a g29. Which only serves to further my point that other curbs and road features aren't being felt properly for those of us with this issue (mostly g29 PS4 Pro users it seems). Curbs etc are completely smooth for me, like they don't exist. I'm assuming whatever is on the Expressway roads is programmed in a different category to curbs etc, and all we need is the rest fixing. Fingers crossed this gets passed to PD somehow!