Certainly more effective against armour than a sword. Of course, that doesn't mean much as swords were not particularly effective against armour. Still, I imagine it would be pretty good. A lot of war hammers/strietpickel were not much larger and had similarly shaped business ends, and the conventional wisdom is that the backspikes on such weapons were designed to defeat armour.

As an aside: I have found that I can deliver more energy throwing a weapon at close range than actually striking with it. This goes for javelins, swords, axes and hammers. I am not sure how this works from a physics standpoint. I just know from experience that I can get better penetration or do more dammage with a throw. I wonder what the typical mass of a wurfhaken is. About a kilo maybe?

Ps- According to Merriam-Webster's dictionary a hurlbat refers to either a cestus (boxers glove) or a javelin thrown with an amentum. ME hurlebat Fr hurlen+bat (Go figure)

My guess to explain the physics of your observation:

When properly throwing a weapon like an ax, knife, or tomahawk, it is held behind you near your shoulder blade and brought in an overhead arc above your shoulder, with the release point (ideally) being at the top of the arc.

When properly striking in the melee, the weapon is brought from a guard position in a much straighter trajectory against your intended target. Much of the strength of the strike comes from your footwork: moving your body forward and twisting the hips.

Due to a slightly longer period of acceleration and a slightly higher component of angular momentum, the overall momentum of the weapon would be greater when thrown than when used in close combat.

Of course, throwing has its disadvantages, too. (not having the weapon anymore is one of the bigger ones).