Note that this comment is made without understanding on how much PG listen to GPF in deciding these dragons (including their level scope, since I hate it…), and merely my opinions about the currently released dragons
I believe PG has their own standard on how strong a dragon / tower / spell is, albeit their standard is often much different from our standard. PG bases their decision on various playing style (including the mighty Ballista).
I believe that a dragon is considered exceptional, if the dragon can surpass PG’s expectation on how the dragon should be used (by wide margin), and what’s really happened in live base.
Narrowing our scope, I feel that Huitzil is an offensive version of Sage. Instead of healing, and economized explosive shield, he has Bloodfury (rage boost) and Explosive Aegis, with offensive abilities, controlled explosion, and more durable shield.
Coatl is more like defensive Equestor with less rage (doesn’t need to hit certain tower for guaranteed shield). Sadly, I think that EE is superior to NL, if one can use it effectively.
Cuauhtli is like an enhanced version of Avyx, if only the runes boost damage, not DoT duration. Its DoT is useful for one who isn’t used to do burst damage, but boost nothing for burst damage (which is said to be the strongest ability of hunters).
For fully boosted dragon, its healing is more reliable than healing mark, as it can fully heal the dragon. However, due to Ice Flak and rage drain (and 2 rage instead of one), it’s more vulnerable.