Also taken into account is that hiding isn't exactly invisibility, which grants 50% concealment even if the foe knows what square to attack. With hide, people either spot you or they don't. There aren't any See Invisibility spells or the like. Blindsense, tremorsense, etc... AFAIK just completely foil hide if the foe has the range and line of effect to you.
Short answer, in my opinion: With hide if the opponent doesn't see you, there shouldn't be any need for a miss chance, because he shouldn't be attacking your square (save for as part of an area attack, where miss chance won't help anyway). If he has a means of knowing you're there, the entire hide's just ruined.