the very nature of what intimidate and diplomacy does has been changed from PnP to DDO.
intimidate is not for gaining aggro in PnP, and diplomacy is not for making monsters hit your friends in PnP.
diplomacy takes 1 full minute to try and make an NPC more friendly towards your group. has your party just walked into a crowded tavern and its all gone quiet and everyone is looking at you? at the back you think you saw some blades being drawn. no problem! let the paladin step forwards and work his silvered tongue so the whole party can drink in peace.
http://www.d20srd.org/srd/skills/diplomacy.htm
intimidate takes 1 full minute to try and make the NPC more helpful towards you. there is a link to diplomacy skill for more information. after you've left the NPC will then be more hostile to you than when you first met them. your following a lead on your quest and the NPC its lead you to doesnt want to talk. with no silver tongued paladin about your barbarian decides to rough the guy up a bit to loosen his tongue. it works and he starts to babble giving more information than you needed. after you leave however the NPC feels resentment towards you for the way he was treated, if you ever meet again he's sure to hate you.
http://www.d20srd.org/srd/skills/intimidate.htm
so, thats why the paly has diplo as a class skill. any paladin trying to convince an NPC to attack his friends instead of him self (assuming there is no cunning plan involved) would probably be stripped of his paladin abilities and become a fallen paladin, nothing more than a fighter. the implementation of diplomacy in DDO is directly opposed to the way a paladin would use it in PnP. getting a monster to hit your squishy friends is something that goes against the strict paladin moral code of conduct.
standing in the middle of battle and getting the monsters to hit you instead of your squishy friends is exactly what the paladin wants to be doing, it fits their moral code of conduct like a glove.
so no Aschbart, the relationship between class and skills has not been preserved, its been perverted.