I see it as more of a trait than a feat, in general. I guess we'll take the middle ground and call it an extraordinary ability, or maybe even a disease.
Though, if you really want it as a feat, I can nerf it, and have characters able to take it more than once, gaining the extra bonuses after taking it a set number of times. (Like Diehard after taking it 5 times, the three rounds past -1 after taking it 10 times), and each time you take it... actually, f*** the rest of this paragraph.
Know what? I'll just rework it as a 10-level PRC.
And I'll fix that Copypasta issue after I sleep.