EDIT: Spark Rock and Rain of Fire produce groggy just fine, and at times DC changes the color of the bar but it doesn't really seem to be doing anything. Odd.
EDIT #2: Slayze, are you sure you don't have the numbers mixed up? It seems Diffusion Cannon, which only has a "1" number in our skill description (no value for the "2" number) isn't increasing groggy at all. But Double Shot, which has values for both, is increasing it. Only explanation I can think of, at the moment.
Edited by Rimmy, 06 October 2011 - 12:02 PM.