if you can not tell by observing other players if they deliver or holding back, you need to watch some more Rick Ashley videos. Seriously most friends I have play the game by sound. They know only by listening what abilities someone is using or when they are getting hit by something.
Hardcore my behind.... dps-ers refusing to perform a certain action like interrupt or something like that, only not to fall behind on the damage meters. Next thing you will demand after damage meters is tank and spank bosses? So you do not have to waste time running around or doing something intelligent, only spam your buttons to have maximum damage output?