Sir Whiskers said:
Then why bother with designing the feat?
See the movie that was mentioned. Or one of any number of other chambara flicks. Heck, see The Princess Bride, even.
One of the staple scenes in swordfighting flicks is when a mob of low-level guys charges the sword-wielding hero, who slices them to ribbons before they can get a swing at him. This is not something that the D&D combat system emulates well.
1) You can do something similar by assuming the mooks close for combat, and then the hero uses iterative attacks, Cleave, GC and/or WWA to drop them all. However, this means the mooks get their shots in first, which is not something that typically happens.
2) The hero could ready an action to drop the first guy who comes in range. However, that's only one guy, and the rest still get to attack.
3) The hero could use a reach weapon. But in the movies, it's always a sword.
4) You could assume that the mooks start just far enough away that a full round's movement takes them to exactly 10 feet away from the hero, who then takes a 5' step and slices them up. But this is just silly.
Really, just because this feat lets you slice up mooks more easily is not something to be worried about. Mooks are typically not a threat to any mid- or high-level fighter, except in huge numbers (say 50+ or 100+). Even then, a couple of fireballs and they're toast. Mooks are there basically to let the PCs show off, unless there are exceptional circumstances to the combat. And the reach guy still has advantages in not having to close the range, and being better-equipped to handle other things with reach.