Berserker's Power not working on Berserk (Resolved, my mistake)

Old post: I was trying out a glass cannon build in PvP and noticed in the UI that using Berserk should yield 3 stacks of Berserker's Power. However, as it turns out, I ended up getting no stacks whatsoever upon using Berserk.

Edit: Nevermind, it seems like I was mistaken. As it turns out, you need to LAND the initial Berserk attack... which is kind of misleading considering that the Berserker's Power UI only stated you needed to use a burst.