I was having real issues sticking to my own posted rotation!
If I cast DnD, I'd wind up short a rune to do Pestilence & Blood Boil. And with ret pallies and mages and whirlwinding warriors, sinking aggro on all them mobs early is crucial to avoid mass hysteria (on my part, I hate having to try to figure out which mob is not attacking me so I can taunt it back to myself, and on the healer's part as they try to keep me and some squishy person alive). Unholy Blight does help a bit with that, but not enough.
Then I realized... duh. I have Blood Tap (and a new minor glyph to consider). Since that epiphany, I've been able to DnD, Icy Touch, Plague Touch, Pestilence, Blood Tap, Blood Boil, Unholy Blight and go! (And need to consider Empower Rune Weapon and see where I can/may need to fit that in.)
Keeping Bone Shield up is harder than it seems. I need moar parry and dodge. Some fights it seems to stay up forever, and other fights within two seconds it's done for.
Keeping mobs in front of me is sometimes an issue, especially if I have to maneuver around to grab something else. Can't parry attacks coming from behind, so that just mows through Bone Shield.
And sometimes you just laugh and laugh when some boss does a magic attack that your Anti-Magic Shell noshes upon.
Thus far my tanking experiences have included: UP (getting away from Skadi is a p.i.t.a.), Heroic CoS, Heroic UK, GD, VoA-10, OS-10, HoL and Heroic VH.
Only once did I have someone say, "Unholy tank? Does that actually work?" To which I said, "Yes."