Yeah, unless the enemy list has absolutely no templates or blasts, DSing plaguebearers is generally a poor idea. *sigh* There's S&P for you. I don't think Plaguebearers can cut it, as nice as touch of rust+poisoned 4+ sounds.
That list generally has some solid hitters, though I would try to bring the 2nd CSM DP over and turn it into a CD DP, for all that it loses out on defensive grenades between differences to "Daemon of Nurgle" between the books, to load up it and the other CD DP with Greater Rewards--those add a bunch to survivability, and are well worth taking two of each, I say. (perhaps leave the 2nd DP in CSM if you take the Nurgle Herald in my later suggestions)
Might drop a Heldrake, given the very tightly restricted firing arc it has these days.
One solid unit I'm not seeing here is the Dronestar: 9-odd Plague Drones who conga-line a Fertility Herald of Nurgle out behind themselves, and run the Instant Death stings. Able to take on just about everything barring heavy walkers and durable as all hell.
Honestly dunno how Beasts of Nurgle play--they look decent on paper, just fall behind the Plague Drone enough not to be worth taking.
If you want something more to DS in, I might consider a GUO. Sure, you already have 3 HS choices, so it would limit your winged DPs, but it would be a hard-hitter that doesn't need to spread out like Plaguebearers would.
What sphinx of plascrete and adamantium bashed open their skulls and ate up their brains and imagination? Imperator! Imperator!