Close...
Read the OP again.
His biggest and best methods of operating is using social skills, blufing his way out of anything.
The wiz/sorc spells from Sublime Chord are only used insofar as to negate Batman Wizard Optimization being one big 'I Win' button. If you don't have a PC doing a Batman Wizard, he can be toned down to straight Bard (or maybe Bard/Fatespinner if you like) and work perfectly well.
The only reason why he has Sublime Chord is because it's the only way to challenge a Batman Wizard.
And again, I would like to point out that the point of Joker is not to 'beat' a Batman Wizard, but simply challenge him and make him expend more effort than two spells + Pre-Buffing.
Batman Wizard has I Win buttons all over the place. He can eliminate any threat, no matter how nasty, simply because he has that much power.
Joker is designed to challenge that build, by negating many of his I Win buttons, and negating and/or countering many of a traditional Batman Wizard's tactics.
Again, he's not supposed to WIN. He's supposed to be defeated... then after that, the Batman Wizard goes... "Wow... I'm out of spells... low on usable resources... but damn that was fun". That's what Joker is supposed to do. Not to beat Batman Wizard... but to give him a run for his money, and make him earn his victory.