Mystic Muse's Marvelous Manual of Monster Class Mania! (3.5 Taking requests)

[Zaydos]

Well, it can already get enhancement bonuses anyway. Or it will once I get the "Hoard" ability done. Also, it's just an armor bonus which shouldn't be that big of a deal. It doesn't boost touch AC, and a lot of abilities don't even target AC at higher levels.

But most monsters (read not PCs) still actually deal with AC and a large boost to your AC (in this case Con +3 over everyone else's) is still problematic. An Abjurant Champion using Greater Luminous Armor will have comparable (but still lower) AC against melee attacks, and significantly lower against melee. A polymorph using wizard will have a better AC but no one else will even compare (minimum of 8 less which means if the high AC guy is hit on a 10 you are probably not going to be hit at all).

And coupled with the 20th level ability your AC is another 5+ points meaning you cannot be hit at all by most enemies and your saves will have Charisma to them as well which furthers the problem since it gives you high defenses against all types of attacks.