I think the OP's mistake is thinking that slayers are primarily a Str/Con class. They're not. Knights are Str/Con; slayers are Str/Dex, which means they get a big boost from adding Dex to damage.
The damage bonus was so large during out play test that the weapon choice was irrelevant almost. Our slayer could have been using a dagger and would not have dramatically changed his dps.
That has to be hyperbole, right? A Fullblade-wielding Slayer with Dex 10 does as much damage as a Dagger-wielding Slayer with Dex 18, assuming that you aren't talking about the Melee Training (Dexterity) build.
Mostly yes, I was just illustrating that the damage bonuses were so significant that the dice of damage from the weapon was just a fraction of the total damage.
You should talk to your DM. I don't have only the players with Bluff, Diplomacy, and/or Intimidate talk to NPCs. I have every player at the table contribute. If a player wants to roll Diplomacy or Bluff, that's ok, but social roleplaying is not typically and primarily resolved via social skill rolls when I DM. It's resolved with roleplaying and possibly an occassional roll if the NPC is on the fence on something.If I were to play a Slayer, I would worry most about the problem that I have with my Knight right now -- virtually no ability to contribute to non-combat situations that don't involve carrying or knocking things down. It gets dreary after a while having every single NPC ignore your character except for slurs and smirks, and never being able to pipe up when there is a lock or trap to finagle, a scouting expedition needing volunteers, a shopkeeper to wrangle, a noble to charm, a trail to follow, a rune to decipher...
It's like going to a big scout gathering and being the only one with no badges on your uniform except the one for good attendance. (Scouts, feel free to explain that gatherings are called "gymborees", that uniforms are called "haversacks", that badges are called "nibnobs" and that there is no nibnob for good attendance. I'm here to learn.)