My biggest problem is, that the fight got changed from a one-on-one duel to a regular battle. This makes no sense to me. The quest description says, that your men ran away and you have to do this on your own, and suddenly they are back?. Changing this back to the way it was, would go a long way in making this fight at least somewhat more challenging.
However, you can't make the fight too hard. Otherwise, you would remove the only other option a player has, if he isn't strong enough to win by conquest or has the necessary infrastructure to go for the Spell of Making and everyone else dislikes him. Still, raising Waerlogas HP to be on par with an Ashwake and maybe adding a little Dodge would make him more challenging without being OP.
In the end, the Master Quest should be won by your champion and not through the help of units. Else it just makes the battle ridiculous...