Level 10 bard needs damage reduction

[Cavall]

That song reduces saving throws by 2. With that, the melodic casting feat Melodic Casting - Therafim and the spell fear, you can lock down a whole group of people.

Thats way better than damage reduction in my books, and only two feats, one a must have for bards anyways.

 

[DumbPaladin]

Dragonskin Decanter (I believe it's called) from MIC. It'll grant you DR 4/adamantine if you use all three draughts in one application (a standard action) that blocks 40 damage and/or lasts up to 1 minute.

 

[Empirate]

Not sold on the Snowflake Wardance thingy. "Any weapon" sounds suspiciously to mean "any ONE weapon" to me. But whatever, it's not really a problem balance-wise even if it affects all your weapons.

Moving on: Doomspeak is an excellent feat to use under cover of Greater Invisibility. It will nicely set up a target for Dominate Person in the following round. Which will change the action economy quite a bit.

In fact, the action economy is the main problem your BBEG will be facing. Maybe you should give him the Leadership feat to attract a Crusader cohort to tank for him or something like that.
Single enemies, especially against six PCs, must often use cheesy, unnerving tactics to not die in round one or two: summon monsters while invisible; hide in an illusion; heavy save-or-die with optimized save DCs; inescapable battlefield control plus damage-over-time AoEs; and so on.