Vile Spew has a 40y range, dealing damage and spreading the two dots. I can't see how it would not be better than Unholy Blight 10y range in PVE (reDOTing every second on PVP could be good, need more info on defensive dispel) if Blizzard don't add some AoE damage.
With Howling Blast infecting with frost fever Vile Spew seems the nobrainer choice for both DPS PVE specs (and roiling blood for blood tank). Can't see how UHB will fit in PVE (again only if they forget some AOE damage in the tooltip)