I think thats Dragons have enough HP yet. Perhaps give them a faster HP recovery (around +50 could be fine) and more MP (between 500 and 700). Perhaps also add some attack when they lvl up. Or do like with others unit, give us some skillpoints to spend, when they level up.
Actually, to my point of view, at the moment, Dragon is more a one time use unit in battles PvP or PvE. Because Dragon is actually very weak and it's quite easy to counter its attack.
Or why not a self heal skill for Dragons, as they lose HP so fast when fighting, and healing them is very long even with echanters.