I'm looking for some math to "degrade" stats over level. The idea is that if you have x value for a stat that it's affect will be less when you increase your level, making you have to put more points into that stat to maintain.
For my specific example I have a stat I call Focus. I want the Focus stat combined with the level to create a percentage. I will use this percentage against each abilities damage/heal value to get a value. This value will act as the low end and the abilities value will act as the high end for finding a random number between. So if "Strike" has a value of 10 and my focus % is 50% then then I find a random number between 5 and 10 to get the actual damage to apply.
So at level 1 ideally this % is 100% (so "Strike" will do 10 damage always). At level 2 with no more points in the Focus stat, I want this final % to go down but putting points into the Focus stat could keep it up.
This seems like the kind of thing every RPG game has, but I'm not sure how it's done. I'm picturing all stats being like this. Each level I would increase base damage/heal values for abilities by x% and then degrade other stats. Like strength for example. The idea would be to try and keep the strength state so it results in 100% of the ability damage by putting points into it each level.
Does this make sense or am I way off base in my thinking on how this kind of stuff is done or can be done?