I found a bug

When having levels on combat NPC's starts taking less damage over time not sure if I messed up or if its actually a bug.

SkillTree.json

Download the latest version to fix that.

Thats the bugged one I had to go back an update to fix it

1.5.7?

No I was on 1.5.7 had the bug then fell back on 1.5.6 to fix it

Looks like even this is doing it now. Its fine for the first 24hrs then all of a sudden its like throwing a rock at a wall but it is doing it on 1.5.7 as well unles I have to re right the config again and thats annoying as hell to do for every bug 

It was patched in 1.5.7.

The issue was due to the math. I accidentally had it set to multiply the damage by the modifier: [scale *= value] which would actually divide the amount.

I fixed it by adding 1 to the modifier to put it into a positive value: [scale *= (1 + value)]

I've not had any issues from other servers that run this after 1.5.7 was released. If your issue persists, try unloading all other plugins to see if the issue is still there.