I posted the following comment over at Gravity's site in response to an excellent review post he made.
I'll have to look back at my posts regarding GOD (Glyph of Disease) and see if I'm clear on this.
.... and I wasn't really, in my post on Pwnwear. But let me clarify here a few things about using this spec for maximum benefit.
The 'normal' 3.2.2 unholy spec doesn't use reaping or epidemic and refreshes diseases every rune cycle. It's become very popular for both 2-handed unholy dps and for DW unholy dps.
The GOD unholy spec doesn't use reaping, and as far as I can tell, epidemic is optional. In any case, the key to rolling diseases is that after you have a nice stack of high-attack power diseases rolling, you don't want to touch your icy touch or plague strike buttons again for the rest of the fight. They'd 'write over' your powerful diseases with less powerful ones.
As Gravity has pointed out, there really isn't a rotation for this. There's a priority:
1. Make sure to refresh diseases with pestilence, preferably within about a second of them expiring, but also right before you have to target switch or you get knocked out of melee range.
2. Scourge Strike spam
3. Death Coil if capped
4. Blood Strike any blood rune not reserved for pestilence.
5. Bone Shield should be refreshed when it expires (I usually blood tap immediately after to not lose that unholy rune for my next Scourge Strike)
6. Horn of Winter if you have an empty global cooldown - for the runic power.
If you've read my blog, you'll see that I really like this spec. I find I'm doing very comparable dps on single target fights like heroic Northrend Beasts to the 'classic' blood single target dps, and if there's even one add, this is considerably superior.
For reference, My current spec is: 16/0/55. I'm going to try a couple variations but this one definitely works well.