Basically yes, if you use a recent
nightly build.
The armor of the dragon has been boosted and the additional problem has been fixed as well. It's not quite the same as in the original game, as fixes to the strength and agility cap, the nerfing of the heal spell and an increase in damage of spells did change the balance somewhat.
Basically the dragon can now hold out against bigger groups quite well again, but in vanilla keeper 1-on-1 against a warlock/wizard the dragon would manage to survive forever because of the good heal spell. Now he dies eventually.
However, if the current implementation of the dragon is the only thing that bugs you, you could easily change him further yourself, by giving him even more armor,
a second heal spell, or increasing the spell power of heal in the config files. This can be done by opening keeperfx/creatrs/dragon.cfg or keeperfx/fxdata/magic.cfg with a text editor like notepad.