http://www.curse.com/addons/wow/affdots
Dots do not update dynamically with your stats. When you gain or lose spell damage/crit/haste/mastery/damage modifier, dots will not benefit from those effects until you reapply them. This addon compares dots on target with your current stats and shows if reapplying dots will make them stronger or weaker.
Download OmniCC addon to have a numeric display of time left on dot icons. I also suggest some addon to watch your procs, buffs and trinkets, like TellMeWhen, WeakAuras or RainbowProcs.
Type '/affdots' for options.
Dot background colors:
* Green: your current stats are better, recasting will have a full benefit of Pandemic
* Blue: your current stats are better, recasting will not have a full benefit of Pandemic
* Yellow: your current stats are worse, recasting will have a full benefit of Pandemic
* Red: your current stats are worse, recasting will not have a full benefit of Pandemic
Most common scenarios:
* Green: cast unless you expect more incoming procs soon.
* Blue: cast if your current stats are significantly better or if you have to switch targets.
* Yellow: cast if you have to switch targets.
* Red: do not cast.
Number is the relative power of your stats compared to stats you had when casting dot, 110 means your dot dps will become 10% stronger if you recast now, 90 means they will become 10% weaker.
If you do not use "Relative numbers" - number on top is dps based on your current stats, number on the bottom is dps of the dot that is currently on target.