I can't agree with you neitherSorry smoky tune, I have to disagree with you about this kit's balance. You're giving the bard most of the powers of being a cleric (access to all clerical spells levels 1-6), none of the disadvantages (highly limited weapon selection), you're throwing in a few goodies besides (regeneration, FTW, though all of the chants are better than a regular bard gets at the same level), and on top of that, he gets thieving abilities. OK, so he can't pick pockets. He's still detecting and disarming traps, using stealth and opening locks. And picking pockets is probably the least useful of the thief skills, IMO. Even a fighter/cleric can't use a bow, but there's nothing to stop a bard from using one.
Though this bard gains cleric spells, he still remains a bard:
He cannot wear armour greater than chainmail, while clerics can use plates.
He uses thac0 progression table for thieves, which is worse than clerics' one.
And yes, what thieving abilities were you talking about?
Getting access to priest spells, he however can cast lesser amount of them per level, and doesn't recieve bonus spells from high wisdom. On the other hand, to tell the truth, this is compensated by his chants, because all of them simulate cleric spells, with less power but affecting all party members:
Sanctum is like lvl 1 Remove Fear + ST bonus
Contegitas is like limited combination of Protections from Fire/Acid/Cold/Lightning.
Consilium is a limited lvl 5 Chaotic Commands but enchanted with Hold resistance. It may seem quite cheesy, especially at lvl 9, but not much actually, provided it doesn't remove already active effects.
Sanitas is a long-lasting lvl 5 Mass cure and lvl 4 Negative plane protection. Gained at lvl 14, it is available only in SoA, where there's plenty of heal-per-time-period items. So it won't be of much importance already. Besides such healing isn't very useful in battle, unlike Mass Cure spell.
Veritas is lvl 6 True seeing.
Here you can aruge that chants have unlimited uses, but actually I can't remember necessity to cast more spells that I've prepared for a well-planned day of adventures. For example, if I'm going to face Firkraag, I get all third level spell slots filled with PF Fire, and all my party gets almost totally immune to his firebreath. When I'm planning to confront mages, I memorize two True Seeing, and so on.
Finally,chants are indeed better than usual bard song, but keep in mind that all of those effects are not cumulative, and you'll gain only one of the bonuses at the moment.
Thereby there's no reason to call this kit overpowered in any way, is there?