PC,
I just had a thought, which wouldn't work with my players, but I'm sure will do great with yours...
You've mentioned in the past that the Defenders have been watched in combat. Is it not also fair to say that they've probably been watched at other times, too?
In which case, when the ghouls actually attack, they're most likely to capitalise on the Defenders' psychological weaknesses. (And you just know your players would play along and make it so much more amusing).
For instance Agar's aversion to insects; if either a swarm of beetles preceded the attack, or if each enemy was coated with beetles, then Agar wouldn't have a clue who to attack (as they'd all be equally terrifying)...
The simplest Legend Lore about Nolin would provide his phoenix background, together with plenty of detail of his past indiscretions. Result? Either cold-based attacks, telekinesis to make the most of it when he explodes, or all the attacking ghouls polymorphed to look like his past lovers.
Malachite's obsession with slaying the undead is a weakness in itself. Galthia could be distracted with visions of Illithids backed with a few psionic attacks.
Just a few suggestions (which you've probably already considered) to make it look like the White Kingdom's been doing its research!