I think you'll be pretty strong. Again, I don't know if you need so many furies. Maybe just 1 unit. They are
LD 2. You can use them to suicide attack something, but a whole lot of stuff is just going to make them crumble almost immediately. You can use the nurglings to guard your flanks.
Another trick is to dump the
lvl 1 on one caster and give him a Staff of Nurgle. It will give you something to throw dice at that actually causes
dmg. And it will directly raise the wounds caused on your Epidemius total. That or the breath weapon. The point is you want to hit the 4+ poison ASAP because your army simply doesn't do much
dmg without it.
A bunch of steadfast, regen 4+, ward 5+, fear, S4, T4, dudes who poison on a 4+ is actually pretty scary. You still never get super hammer-y, but you hope to take less wounds and hang around. Depending on who you are facing, you might reform from 5 across to a horde formation when you get the poison bonus. That way you can have 3 ranks of attacks who auto wound on 4+.
Just looked up in the
FAQ
Q: Do Poisoned Attacks that wound automatically on a To Hit roll
of 5+ or better still need to hit to cause a Wound?(p73)
A: Yes
So, there's still that. When you get the 4+ poison, you would auto hit and auto wound anything with
WS of 1-6 if you roll a 4,5,6, regardless of toughness. So about a 50% chance to hit and wound anything in the game on every single attack on your Core troops. And the S4 of
PB is -1 armor save. That's great stuff. Which is why you might want to reform to Horde to get an extra row of attacks in.
Let us know how it goes.