It is especially annoying that they don't utilize some very nice benefits.
Like the energy based dragons (only the melee wyrmguard of each dragonflight it seems)
have no spammable energy consumer. so while you can take "Go for the Throat" in marksman, it does 100% nothing. your pet always has enough every to spam every ability on cd, but will also spend its entire time at full energy, with or without the talent. (so no point to include tamed dragons on this talent)
The mana dragons being able to receive replenishment is good. they can also get lifetap if you take Mana Feed (demonology)
but you can't benefit from Invigoration (beast mastery) with anything but a tamed beast, and Go For The Throat.. should restore mana to the various pets as appropriate.
As such, tame dragon is strictly inferior for.. basically every build that might want a pet. no dragons are good enough to use 6 ability points, and talent points to potentially support it. its like a semi-thoughtless dot that deals around 50 dps.. with a terrible scaling ratio.