Rankings are based on the following priorities (not rotation!):

1) Icy Touch & Plague Strike to maintain diseases
2) Dark Transformation
3) Death Coil on Sudden Doom or Runic Power > 90
4) Death and Decay
5) Scourge Strike
6) Festering Strike
7) Death Coil

Use these cooldowns as often as possible:

1) Unholy Frenzy
2) Summon Gargoyle

Stat Importance

Strength > Hit (to 8%) > Haste > Mastery = Crit > Expertise

Reforging

1) Reforge your weakest stats until you've reached 8% chance to hit
2) Reforge to Haste as it has a slight advantage over Mastery and Crit