Already balanced. If the cleric favors Strength over other abilities (say Wisdom for example), then so be it. Fighter might be favoring Dex over Str, or may favor something else entirely. Nothing needs to be added to balance it..
My point is with flatter math, it makes it easier to get to unexpected results. A few good rolls of the dice for ability or too high a point buy and something could break. Cast the wrong buff spell or find the wrong item and poof! their/cleric/druid/wizard/farmer/housecat is a better warrior than the fighter.
If feats are still in, perhaps Skill Focus on whatever skill(s) you want to excel at. No need to scale skills/DCs to high numbers like before.
That sounds like a feat tax. My level 20 rogue/bard/assassin/ranger should have to take 3 feats to do epic stuff.