My games are limited, but thus far -- yes, they seem to be doing OK.
Plaguebearers are not very killy but can be a pain to shift off objectives.
Plauge drones work very well.
GUOs are good.
Nurgle
DPs are amazing
You might need to add some soulgrinders, plauge drones, plague marines, etc...
Play with it and see.
Here are a few pics of my
WIP nurgle army