Except that any "munchkin" stupid enough to take this class will wind up killing off his party. It's not a very good PC option, more a BBEG fighter build.
I'd suggest knocking Improved PA down to +5 for every -2 to hit, and Greater PA down to +3/-1. That doesn't seem too bad to me; in fact, if you run the analysis, it's likely to lead to an FB Power Attacking for about -4 (+12 damage) against a foe of appropriate AC for its CR. Considering that FB is a melee class, that damage is the only thing it does, and that there are ways to counter this (using Combat Expertise will make PA a suboptimal choice even with these numbers, and there's that nifty new tactical PA-negating option), I don't think that would be too outrageous. Just IMHO...
[The other fix that is badly needed, incidentally, is for Deathless Frenzy. I'd suggest allowing it to function until the FB hits a negative hp total equal to his maximum normal hp (not counting rage or frenzy bonuses), at which point he be pushin' up de daisies.]