Here's what I did...
You can make a "diplomatic" character in NWN2: I made a Paladin (which has to have a high CHA anyway for some of his abilities), gave him a 16 CHA; his skill in Diplomacy is 8 or 9, at the moment. You could optimize that even further: there is a background feat you can take at lvl 1 which will give you a +2 to Diplomacy.
As it stands now, I have actually been able to talk my way out of about 50% of the scripted combats that have come along so far (with a higher success rate among other scripted events), by using the Diplomacy option (because of the alignment restrictions for Paladins, I don't want to do anything "non-do-gooder" meaning I'm not picking the Bluff or Intimidate or Lie options...).
Wisdom has presented an option every now and then, but it's infrequent. If you're making a "diplomat", you will most likely want to focus on CHA; then pick Bluff, Diplomacy, or Intimidate, and put as many skill points as you can in that skill at each level (you could pick more than 1, but you really only need 1 to succeed when the option is given to you).
(You can also take feat that will allow a skill focus on Diplomacy, Bluff, or Intimidate, for another +2 to the roll; I believe there are other non-background feats which will also add a bonus to those CHA skills.)
I find it helpful to pick characters which are already going to need a high amount of CHA: bards, sorcerers, or paladins. You could do Rogue (a great option for the skillmonkey-type character), but with those characters you will want to prioritize DEX before CHA, at least for this game.
I hope that helps some.