Hum, bluff and diplomacy rules are borked. Everyone knows what happens when you start interpreting them to the letter... Just BAB + 1d20 + sense motive is more than enough to make feinting hard enough as it is, especially at later levels. For exceptionally well described feints that actually make sense, a kindly DM could give a +2 to the feinter, or for a bad one, a -2, but i don't see it going much farther than that...