I would say it's quite decent. A good mage won't let himself be easily defeated. It's not that easy to take him down with a barbarian's kick. Because the mage's HP also increases, don't forget. And this is no longer that weak mage with 100 HP that you hired in the tavern. And he also provides benefits to the entire army!

And teleportation is great. But first, the barbarian needs to either a) level up (which, excuse me, is level 3 for Haven!) or b) find a scroll (which is even more difficult because it might not even be on the map). So, if we follow point a), it's no longer a barbarian, but a battle mage!