Actually, it seems that he's 36! So, given that the voice actor is actually roughly the right age for the character, I guess that most of my 'wtf' is due to the fact that it's Zuko's voice rather than a 'the voice actor is too young to play that role'. Like you, I'm betting that the more he talks, the more I'll get used to it. :)
no subject
https://en.wikipedia.org/wiki/Dante_Basco