Nice to see I'm not the only Nurgle fan over there. I've been trying some mononurgle lists for the last months, and I think I might give you some advise:
- My main advise: On the Great unclean one: It is mandatory to have the pestilent mucus. Why do you want noxious vapors when you got 10Wounds? no one is going to kill you before you strike back. In fact, combine Nurgle spell number 1 with pestilent mucus, and if they manage to wound you with 1 attack of S1, they have to do a T test with T1 or take one wound. That's amazing!! Consider it, please
- The nurgle heralds need the breath attack! that gives you many combat points, you can kill up to 8-10 enemies with a lucky roll when repeating to wound with the banner. I usually play Nurgle heralds only with that. 140 points is enough.
- I also agree on dropping the greater icon of despair. Although its good, it doesnt have any sinergy with the list.
- I haven't played the Soulgrinder in fantasy yet, I got mine from FW the other day and I'm still painting it. However, I think it is a good support to a monogod army, in particular: Nurgle!
- Beasts of nurgle work well, On a tournament last month I played a unit of 3, and it was awesome!! they managed to kill a horde of 60 zombies in one game, some small empire units in another, and stayed many turns agains a Plaguebearers unit in the last game. They are tough, quite fast, and 3D6+3 attacks are a good reason to take them, despite their high cost.
- And last, I think the PB units are very large. I dont like playing hordes because they are easily redirected and focused. Maybe 25 and 29 is enough to keep on kicking, with 6 man front line 5 deep.
To sum up, I'd drop some plaguebearers, some items from the heralds, maybe a unit of nurglings (youll make more with the GUO's spell), and get a 3 beast of nurgle unit and a soulgrinder
Hope you find useful some of my opinions. Good luck!!