I found DW Frost to be superior for leveling (and DPS) if you have access to heirloom items. You lack self-healing, but the amount of damage you can dish out, especially to multiple targets, outweighs that tenfold.
For soloing elite/group quests, I recommend Blood, though.
Basic Blood rotation is: Icy Touch > Plague Strike > Death Strike > Heart Strike x2 > Death Coil(s). Rinse and repeat for ezmode, or throw in two extra Heart Strikes instead of the Death Strike in the next rotation (since Death Strike should turn an Unholy and Frost rune into Blood).
For Frost, just get the Glyph of Howling Blast and spam Obliterate, Blood Strike, Howling Blast and Frost Strike whenever you feel like it. The glyph will keep Frost Fever up on everything it hits and for soloing I found that I couldn't be bothered with Plague Strike at all, simply because stuff died too fast. Obliterate critting on both weapons with heirlooms is almost always a one-shot, at least at lower levels (read: Outland).
Edit: It should be noted that with a Frost spec, you should apply Frost Fever before using your attacks. I dealt with this by using the glyph and opening up with Howling Blast, then Obliterate and two Blood Strikes, if stuff was still alive. Change Blood Strike to Blood Boil if there are more than two targets.
Edited, Aug 3rd 2010 1:31am by Mazra
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