So Tiger, Dragon, Phoenix eh? Just missing the Turtle. So if we go by strength it'd probably be Kyouka (Knuckles), Ayane (Brawler) and Rino (Katana?). But I'm betting Rino probably has more brains than the other two. Typical Megane archetype.
Its not a manga about dragons. Its their skills or fighting spirit I should say that resembles dragons. A manga with dragons in dragon magazine. Priceless.