They are best used as a source of income.
Allow fighter into group with full WBL.
Allow fighter to actually fight in a cage match with an Astral Construct (and thus die).
Take WBL.
Repeat.
Fixed.
Jokes aside, while an optimized Fighter is better than a non optimized one they still aren't going to bring much to the table. At best they're a generic DPS. And as anyone who has ever played a game that uses that term knows, if a DPS dies no one really cares because they are redundant and not especially important. They can at least be a good generic DPS, but even then other things are better. Trying to do other things will just result in you not being able to do your job, such as playing around with expensive, time consuming, low DC poisons that don't work 95% of the time or more.
The few skills that are good are also low DC stuff. Sure, you can make the DC 10 checks to manage your Magebred Warbeast Fleshraker easily, but at that point you're just running your own replacement character, unless of course you avoided falling into the trap of gimping your character for skills. And since it is only DC 10 (or 8, if not injured) anyone else can as well.
This is also true for Ride, though that is probably a good thing in that case as non class feature based mounts aren't going to keep up at mid and high levels anyways.