The quick fix for this is to add a prerequisite of Greater Weapon Focus. This feat was intended, I believe, to bolster the fighter's ability to damage and even the playing field a bit with the wizards and clerics. Now, fighter is actually a valid choice for all 20 levels because there are that many good feat choices out there. With only the core books, the fighter runs out of decent feat choices. Still, I'm not sure it's a big deal if someone dips into fighter for 4 levels to get this feat. No one's tried yet in my campaign.