[QUOTE=Melondar]I'm trying to make a HoF party with just 3 PCs (more challenge, faster advancement, and I don't like dealing with 6 characters. 3 seems like the minimum I would need to do HoF.) It seems like the three best characters to have for this would be your characters 1,3 and 4. Here's my dillemma: One of these three characters needs to be the "diplomacy" character, and none of them have both high int and cha (which are both needed for that.) [/QUOTE]
you should think about adding a 4th party member, adding PC 5 isn't a big deal and you even advance faster if you keep her at level 6 to 8, even have more challenge, as you need to protect her all the way through the normal game and she doesn#t need much management...-...and is the perfect diplomat even at low level...
[QUOTE=Melondar]I figured it would be possible to take the Pal/Sorc, lower her WIS to 4 and CON to 10, and raise her INT to 18, so her stats would be 10/18/10/18/4/20. Although I'd be sacrificing a huge amount of HP, it shouldn't matter too much, as I can probably get her AC above 60 anyway (and use the Pal/Clr as the main tank for tougher opponents.)[/QUOTE]
CON is an important stat for caster!
[QUOTE=Melondar]My two questions are this:
First, is there any huge disadvantage (other than penalty to saves) that I'm not realizing I would be taking by lowering WIS to 4?[/QUOTE]
for an arcane caster - no - but you will miss quite a lot of will saves!
[QUOTE=Melondar]Second, would I, in fact, be better off with 10 DEX and 18 CON, which would give me 120 more HP, but allow more opponents to hit me (and more often)? I'm thinking since this character could just cast MI anyway, she'd be better off with the DEX.[/QUOTE]
I would go for DEX but only if there is absolutely no other choice...
[QUOTE=Melondar]EDIT: I just realized that you can only decrease WIS to 5 with an Aasimar, but also that you only need 16 INT to get all of the diplimat skills plus concentration, so it works out. You only need 14 INT if you forgo intimidate, though I'm not 100% sure if that's a good idea.[/QUOTE]
...just try a 4th party member...
[QUOTE=Melondar]I also noticed that for the Pal/Clr, you cite Combat Expertise as being an important feat to have, but she only has 3 Int (13 is required for the feat.) Is there some way to get this feat without having the required 13 int? [/QUOTE]
...sorry - just a "copy and paste" mistake!

there is no way to get this feat with less then 13 INT!
.