overall accuracy has decreased
This is bad, because of multiple reasons.
First of all, seeing multiple 0's being hit one after the other makes combat a lot less enjoyable.
Secondly, reduced accuracy, or boosted enemy defense, makes XP rates go down when fighting high-level monsters. This forces high-level players to fight low-level enemies if they want to train efficiently. Furthermore, all the high-levels training at low-level spots will steal the training areas of low- to mid-level players. So instead of reducing accuracy, buffing enemy HP should be considered, or the accuracy should simply be changed back.
Thirdly, combat levels. They exist for a reason! A level 90 enemy in place A might be much more powerful than in place B or vice versa. Most of the enemies in Emps are much more powerful than their combat level suggests. This doesn't really have anything to do with nerfed accuracy, but it is something that should be taken into account when future combat chances are being made.