Training is a bit overrated skill in my opinion. As a warrior, you may want to raise it up due to the excess of might runes you have, but for a Paladin and Mage, the pet dragon plays more of an utility role. This is why I usually leave it to lvl 1, because I use the dragon often enough to keep it on par with my char's level.
This tactic is also supported by the fact that pet dragon's level is relevant to your own level in terms of XP gain, so excessive XP boosts aren't all that important in my opinion, not to mention the fact that as a Paladin or Mage, you have less rage and you need to be careful. Besides, you'll be killing dragons sooner or later (and the medal will boost the dragon XP anyway), so dragon XP will not be a problem at all.
__________________
|