Good discussion. I didn't even know the thread was still active after the first reply.
Anyway, something exceedingly nasty, but allowable if one were to toy with the EldGiant's initial skill and feat selection would be to give him a full 10 levels of Ur-priest.
That sort of villain would then have access to all sorts of new options and still have the same CR (and one less HD than the Confessor no less).
After having it explained to me, the non-associated class CR rule makes sense, but some monsters seem to benefit from a great deal of classes. An EldGiant's associated classes are what?
Sorcerer and Wizard caster levels don't stack with the EldGiant's Spell-likes, nor would rogue or bard be feasible. Fighter and barbarian would be associated, but the best class that I'd want as an EldGiant would be a cleric or cleric-like class. It plays to many of his strengths as it is -- especially a continued expertise with combat, healing magic (and don't forget that he could use high level disposable scrolls to get power over his 11 levels of cleric.) All in all, I think the Confessor (and especially an Ur-priest) are tough if played right.
As a note, I have not DMed or played in a campaign that has gone past 12th level. So much of this is predictive analysis.
Thanks,
C.I.D.