@cheezal you need to stop thinking a Diplomacy as a roll and a check on chaîrt. Two reason why that is not how it should work. 1. You shouldnt know how well you do, this skill does not give your ESP you got no clue what your saying is working or how well exactly it has worked! 2. If it worked the way you wan it all you do is max skill take feats gets boostscto get +35 now every single npc ever in the game you meet in regreadless if lvl stat or anything.
What you dont take into cobsideration is the situation you put the person in if do help you, it the penalty for helping outsider is death dont you think there shoukd be a modifer for them to risk life for you? And the more wise a person the harder it should be just influeance like some common peasant. Those two factors have to be entered when using that dip chart