Improved Crit was multiplying other bonuses. This was wrong.
The new method works for base weapons, but it fails to take into account any special weapons. For example the silver flame bow is a special weapon that has a base crit range of 19-20. When improved crit is applied this weapon should go to 17-20. It does not. It only goes to 18-20 because bows are only getting +1. Yes it is still better for crit range than other bows, but it is not applying correctly.