Based on the 5 days i've been playing now, i've come across a few things I dislike about FH2...
1: The "AI". Besides trying to ram me off the road every other corner and having no spatial awareness, they also have the horrible feature called Rubberbanding. Rubberbanding for me sucks the fun out of racing, it was especially telling when I was racing my McLaren P1 hard as possible and a car just breezed past me. Or me racing a stock KTM and having another pass me at about 170mph when the car only really goes 145mph.
2: Cross Country races are too prelavent in series that don't suit them. I don't like having to race supercars offroad much. Some classes I understand outside the obvious ones (Rally/SUV's) like Retro Saloons and Hatchbacks.
3: Some more visual upgrade options would be nice. Maybe some more "Forza Wings" of different sizes.
4: Sound. Almost all of the sounds are fantastic in this game. One that I miss though is the nice echo effect from Forza 5, racing down the S/F at Le Mans sounded epic in any car. FH2 had soo many opportunities for this. Small problem but I liked it.
5: Missed oppotunities. Working Convertables, perfect game for it. Who wouldn't want to drive in south france with the roof down incar while listening to the exhausts?
I probally have a few more gripes, but that is all I can think of at the mo.