I was actually talking to Hafrot of the rawrcast about this very thing. If you glyph with disease where the diseases get refreshed on your primary target when you use pestilence, you can save the valuable deathrunes for heartstrikes instead of reapplying 2 diseases. It actually does wonders for your dps so you can pound out as many heartstrikes as possible.

Check out his build on Staghelm sometime, the dude knows his blood dps.

Oh, that I understand, but still, the longer you can wait to use Pest to refresh diseases the more room you have to HS/DS your way through. Every point in Epidemic is two GCD's.

Whereas, giving up one point gets you Vamp Blood which is entirely survival bent, it offers no increases in damage at all.

The rotation with blood + GoD is pretty simple too:
Step 1: Apply diseases.
Step 2: Frost / Unholy runes = Death Strike; Blood / Death runes = Heart Strike / Pestilence depending on whether your diseases need refreshing (5 seconds or under left). Death Coil if it won't drop you below 25 Runic Power (for the DS glyph buff).

It's a 51/0/20 spec, he can't take the point out of Vampiric Blood and put it into Epidemic, that point would have to come out of Dancing Rune Weapon, which I'm assuming he wants to keep. Not that what you said about Epidemic is wrong or anything.

Well, why not take the points in Improved Blood Presence and Vampiric Blood, and put them into Blood Worms, for additional DPS and minor healing?

That's how my spec looks right now, with the 2 points in the bloodworms, but I must say, on a boss fight, the dps they do is practically nothing. I've been thinking of moving those two points somewhere, but I just don't know where. It's too bad that for dps, there's really only 49 talent points worth having in blood. Having a "Last Stand" might be nice.

putting points into tanking talents (such as will of the necropolis and vapiric blood) is a total waste for a dps spec. especially if you're at all serious about your dps.

why not put points into blood worms? the added dps from them is way better than a defensive cooldown (as dps obviously). if you're spec-ing into defensive cooldowns as a dps spec (in pve), you fail. or maybe your tank fails at threat generation. either way, don't do it.