Death and decay (1 blood, 1 frost, 1 unholy)
then select the character with the most hp or the strongest looking 1
cast Icy touch (1 frost)
then plague strike (1 unholy)
then pestilence (1 blood)

using all the runes then leaving a bunch of dot’s/aoe’s then i usually use blood boil a few times mixed with death strikes.

Yes, in a heavy AoE situation you would use Death and Decay–this rotation guideline is more to show the difference between the rotations of the different specs. Expect to switch things up as the situation necessitates–that is the key to being a good player.