I was wondering, what runes should I use for my MM necro?
Superior Death so you can always have Death at 16. The rest is basically up to you. Some people like to put in Superior Soul Reaping, but I personally never use, and have never needed, more than 1 Superior at a time (not including Superior Vigor) for MM.
Sup Death, Sup Soulreaping, that give me 16 death and 15 soul reaping.
i use a magor soul reaping, and a sup death. WIth this set up, botaks claw and the colletors +1 offhand, brings my helath to 420.
Definitely superior Death Magic. As Bel Ebih has said, the rest is just personal preference. I stick with a minor Soul Reaping because frankly, with all the dying enemies (not to mention your own minions), you'll have an overdose of energy during combat even with just 10 Soul Reaping (I have 13).