[Jack Simth]

There's actually a fair number of mitigating factors:
1) He lost a LOT in the stat department - went from something like a base dex of 18 to a base dex of 10 (which is a -4 to his AC and a great many of his skills); granted, his base Str and Con went up (11/12 to 13/13), but that's not going to make nearly so much of a difference.
2) The shapeshifting isn't so bad - primarily because it's limited to forms of Medium or smaller, and humanoid/animal only - about the worst he can do, combat-wise, is a black bear; the ability is roughly equivalent to that of a 5th level druid's Wild Shape (but more often, and permits humanoid forms), maybe one of the hybrid were forms; for the most part, he's better off fighting as a Wyrmling Silver dragon.
3) It can still be undone, after; the Dragon HD anchors the spell - get rid of the dragon HD (by, say, killing and ressurecting him; most recent level goes away - goodbye dragon HD) and the spell ceases to be anchored, and is again subject to dispelling. Also, see next to find out just how simple it might be.
4) He's immune to various effects... but he also takes extra damage from fire (+50%), which is one of the most common elemental attack forms; even if he Evades that Fireball successfully, he's still down to the point of a normal person's successful reflex save. As he doesn't have Improved Evasion, if he fails his reflex save, he's pretty much toast. An Empowered Fireball from a 10th level Sorceror deals 10d6*1.5 (average 52.5 damage); against Kibin, that's increased by a further +50%; he'd take 70 damage (on average) (D&D math - 10d6*1.5*1.5=10d6*2). An Empowered Scorching Ray with a caster level of at least 11 (no reflex save....) would deal 3*4d6*1.5*1.5; average 84 damage to him. Toasty, no? If that's not enough, an Empowered Delayed Blast Fireball from a Wiz-17 would deal 119 damage (on average) to him on a failed save, and 29.75 (again, average) on a successful save.
5) He can fly - but it's only Average maneuverability - Kaylin could do better with a simple Phantom Steed (3rd level spell) which, at caster level 15th, that's 15 hours of Fly 240(average). Granted, the Phantom Steed can be taken down with a few arrows, a Dispel Magic, or a Fireball while Kibin will still be in the air after such - but a few drawbacks are expected for twice the speed, no?
6) He gets darkvision 120 and 4x the normal dim light vision range as a human - but he had Darkvision 60 before, and little of the campaign has been taking place underground where Darkvision is particularly useful anyway.
7) It would drop him a level behind - at least for a while, although he's slated for that anyway.