The Howling Blast target takes 20% more damage.
The splash damage should be the same, roughly 50% of the main target damage.
Frost Strike goes from 110% to 130% weapon damage.
And Blood Runes are permanently Death Runes.
Meaning we can:
a) take our worst DPS move out of the rotations -- Blood Strike; and
b) use either an extra Obliterate or Howling Blast and Necrotic Strike, in every other rotation (whenever the runes would be Blood and not Death Runes).
