As you can see in the screenshot below I use DoTtimer to check the duration of my debuff on the target. However I really like the way the default Blizz UI does it (By making your debuff always first on the list and making them slightly larger). However no unit frames I found had that option available.
I have found one addon (TuckUnitFrames) that seems to have the option I need but I don't like the way it looks.
Of course since I'm quite used to Pitbull now, some sort of module for it that would add the functionality would be the best solution.