I prioritise howling blast over necrotic strike. Being a ranged spell is so important for early pressure and I actually prioritise frost strike over necrotic strike when in melee to try and get the first kill.

My only other rotation is single target dps which rotated hungering cold and opens with outbreak and empower rune weapon then unloads 3 x obliterates. If I am playing a melee heavy team I will open with the howling blasts then when I get targets in melee will convert to the single target rotation. I often find that switching my target after the initial salvo will quite often overload or confuse the healers to the point that my second target dies without a heal.