When meters are (fully) allowed: "Your dps is low."

When meters are not (fully) allowed: "You might want to make sure you're keeping up Heavy and Chaos Thrust." (Hopefully after having actually noticing this, rather than just giving frequent reasons.)

The difference is that you don't just need to know that something is bad, but also the reasons (which could be given in alternative to 'my parser says so'), which are far more useful to the person doing poorly.