I tried out the Offensive DK Blood build. I went for 20% Haste, and kept close to 200% mastery raid buffed. I did the first four bosses last night in 10 man normal. Healers weren't complaining, discovered I need better CD management, and I didn't die on bosses fights. The nice thing with a haste build for me is that it feels a lot like DW Frost from Cata. Quick hitting, runes always refreshing and always having RP to rune strike. Threat went way up, DPS almost doubled. I'm still picking thru logs, but so far, so good.
Thanks for all the advice people gave, and all the people who contacted me in-game too. Best of luck to everyone.
You'll get the same feel with pure avoidance as well, and you will certainly do more damage. SoB proccing on avoidance in addition to attacks is fairly noticeable. I was swimming in RP when I had 25% haste coming into 5.4, and I am still swimming in RP when I dropped down to roughly 8% haste. The only difference being that I dropped mastery, gained like 10% avoidance and 15% crit. DPS went up substantially and I really don't 'feel' squishy at all.