Not sure off-hand.

But, if you use the priority system, which is essentially mashing six keys together.
You can prioritize which are cast, because there are more of a given spell than another spell.

At the same time, you don't need to micro manage your runes.
Which would be a real pain, with four Death Knights.
Honestly, it is a lot easier to mash one key (which is six keys), than to manage runes independently on four DK's.



Sorry if my answer basically dismisses your question.
Was not my intention to do so, but that is my take on the rotation and tracking runes.
I'm not sure of an addon that will do that.