When I was messing around with Blood and Frost.

I found Blood survives longer.
But Frost kills things so much quicker.

Overall Frost was superior because while my toons could die in less time, they'd easily kill a number of opponents who would take much longer to kill my Blood spec toons (but who would kill the Blood toons).

Experiment and see what works for you.

Once you get Howling Blast.
Your rotation is a priority.
Howling Blast (Frost Rune) > Frost Strike (Runic Power dump) > Necrotic Strike (Unholy Rune).
You don't need to use a Blood ability, because they're permanently Death Runes for you.
You can mess around with Death Coil (lower priority than Frost Strike) as another Runic Power dump, for when things aren't in melee with you.

Here's my setup, which might help you: http://www.dual-boxing.com/showthread.php?t=37658
Note: You don't need Blood Strike any longer.