Dude this card is awesome! Slow Dragon control decks were having huge problemswhen playing from behind in my opinion (Hungry dragon was basically unplayable against aggro with board). I think Dragonpaladin just got playable with this!
I do wish it got the taunt regardless and you only needed the dragon for the +1 attack, but I'm feeling the new dragons they've introduced. We still need a solid 8 drop dragon(I'm sorry, chromaggus just doesn't cut it), but the curve is filling out nicely.
Should work well in control mage if they want to run freeze spells and taunts over water elementals. Also dragon mage always seemed good and with coldara the control dragon deck could be real. So this is definitely viable there.
I'm running two Sen'jins in my Dragon Paladin as an anti-aggro tool (because 5 slot is to crowded to run Belchers), so this absolutely fits perfectly into Dragon Paladin. Not just that it has better stats than Belcher for the same mana cost, but it is also another Dragon (x2) in deck for the Dragon synergy.