What he's describing is a bug and it happened to me yesterday. You get no visible cast bar for Ultimate Power, that happened a couple of times (although it would show up on the focus target bar if you enabled that), and despite being against a wall, the entire party was knocked out of the instance.
Not working as intended, no.
The 'invisible' cast bar is an annoying bug. But it just means you do it old school. Unlimited Power has a -very- distinct animation. Interrupt when you see the animation and you'll be good to go.