Im not sure but I think that's the calculation they made to prevent spamming skills.
You can go to GameServer/Skill.cpp and look for the function isReady(), you should see this:
Code:
reusetime = reusetime * ( 150.00 / (150 + prob )) * (100.00 / (100 + prob));
Delete that line and add this:
Code:
reusetime -= reusetime * prob / 100;
if(reusetime < 0)
reusetime = 0;
I think that should solve your issue, but im not really sure, tell me if its working or not.