I just got a CX bike to be my winter beater road bike / light duty trail bike. It takes 2-3x as much force to pedal backwards than my other bikes. It's still not a lot of force, but it just feels weird as I'm freewheeling it to lube the chain.
I took the chain off and pedaled the crank with no chain and it felt fine so it isn't the bottom bracket. Could it be the derailleur or rear hub? I tried it in every gear combination, same result. The bike only has two rides on it and it felt the same with 0 miles as it did after two rides. There was not enough b-screw tension when I first got the bike (chunking sound in the biggest cog) but that has been fixed.