I have been involved in a few discussions, both here and in the real, concerning fighters and how well they function at mid to high levels.
I believe, that for the most part, fighters work well at all levels. However, a few minor tweaks might make them not only more attractive, but encourage people to play them all the way to 20th.
1) Class skills to 4 ranks per level
Fighters are pretty well the only class that did not gain any benefit from the skill consolidation. Rogues get 8 skill points, and benefit from 6 of the consolidations. I, among others, have had all the classes have gain 4 skill ranks per level, with no adverse effects, quite the opposite.
2) Increase Will save to a good save
One of the biggest annoyances with playing a martial class, is when you get charmed by the opposition. Having a stronger will save would help on this.
And/or at 8th level, have a new class feature, Dutiful or such, add in ½ class level to saves vs mind affecting spells/abilities.
3) Damage Reduction, have it be incremental, every 4 levels increase by 1. This will show the fighter's toughness gradually, rather than all at once.
4) Perhaps allow accelerated healing, due to their endurance/stoic nature/training, based on their class level, say add in .5 to the multiplier every 5 levels. This means that at 20th level, a fighter heals up naturally 3 times faster than a non fighter.
I do not believe that any of these will change the fighter in any radical way, nor affect combat in a large way, except passively.
What does everyone else think?