Shield breaking weapons should not have be stunned when hitting shields, this would be silly and a uncalled for nerf to weapons that are barely used as it is (maybe they are common in NA i dunno, barely see them in EU though).
They are also not op at all, they break shields and hit hard yes, but they dont have good thrusts and usually pretty shitty reach aswell. Using a Hafted Blade is better than a long axe anyways, or using a spear/awlpike compared to a Long war axe. And for 2h weapons having the thrust is such a big advantage compared to being able to break shields faster.
IMO Long axe is better than GLA, because my build has high athletics so i can make up for the lack of reach. But i still find GLA to be a really strong weapon, having good reach and crazy damage. As for the shieldbreaking part i feel they both break shields at about the same rate.
Again, the lack of unbalanced tag is huge in what makes those weapons what they are. Also I find it funny there's no mention of the Long War Axe in this thread, mostly because it suffers a damage penalty for not being unbalanced.
The long war axe is probably the best out of the polearm axes, because its a nice balance of speed and length.