I've recently started to enjoy the powerhouse I can get from being a blood spec DK. I went on my first raid as a full Frost DPS death knight for both Imp Icy Talons and Frost Aura. Since the Aura is overwritten by other, better resist auras I didn't need it. The dps I did my first raid lacked a bit. (Being in quest gear didn't help that by much, but still...)
My second raid I specced into a heavier Blood/Light frost build. My dps jumped up a bit, but the other dks I were with were either unholy or full blood. There was a bit of question as to why there wasn't an icy talons going up since that's what I was yesterday.
To really help your group, pick up rune tap and glyph of rune tap. 10% of everyone's health every 30 seconds is why blood is by far one of the best raiding specs for dk.
Ignore sudden doom, you will get more production out of 5 points in other places.
Best way to help your raid is by not hamstringing yourself. Don't stretch for imp icy, finish your damage build. Post patch your aura heals will be giving 2/4% and with vampiric touch 3/6% for 20 seconds. This ability alone will give your group the longevity to kill any boss.