I would have to do some really deep diving, but I think the whole process has so many areas where Funcom is trying to control RNG based on the roll %, that it really ends up being even more fubar RNG. And i would have to verify , but I think it is set up not to give you a point in every stat when they level. And i think the % really just line up the order everything roles. So highest % rolls first, and so on untill on gets a hit. The problem with that is the lowest will always get a hit if the other 4 :“failed”. hence why it seem that the 40% seems to be “hitting” more than it should.
Example
STr 80%
Agi 60%
Vit 70%
ACC 40%
SRV 50%
I think it rolls, STR, Vit, Agi,SRV, ACC in that order for thsi lay out.
So if STR, Vit, Agi, and SRV miss, ACC has to get at least 1 point if you level. Then since it got the 1 point, it gets the “free” roll and could possibly get a second. Again, just a guess, but i have seen games use the weight “skip” mechanic, and if 1 point is guaranteed every level, then the last one is the fall back if all others fail, and the 40% has nothing to do with it.
Side note, I have seen 100% not hit on some levels. Which means 100% is not 100%. so it just might be like ■■■ panther cologne from Anchorman, but reversed to 100% of the time it works 60% of the time.