It will be a bit odd. We haven’t seen a hammer on a non-heavy armour profession. Given that the heavy armours are mostly metallic, the metallic sheen added by Juggernaut sort of fits with those. But I’m not really sure how it will turn out with medium armour. It might just make it look all metallic.
In any case, I at least hope they add some legendary weapon effects to the skills. Poor shield still has zero love, even though they did a bunch of updates for the other ones.
As someone who used the Juggernaut on a warrior with the arcane outfit, I think it would look neat on leather armor too. The effect of that Legendary isn’t just your armor’s metal becoming shinier, it’s actually the quicksilver inside the hammer’s thermometer that goes out and covers your armor. So, yeah, it works as well on fabric or leather.
I’ve made a few screens with non-metallic outfits and Juggernaut effect so you can see how it renders :
