Focussing Stone, concentration or brilliance, doesn't seem to do anything

I appreciate the focussing stone is something for lower level chaps. I thought I'd give it a go though, just to add a bit more oomph for those key moments where every little helps. The stone seems to cast concentration (or is it brilliance) (and malediction), but I don't notice any improvement in focus, or skills that use focus.

Must be missing something obvious!