A couple of suggestions, feel free to use or ignore as you wish
Change the wording of nurgles rot from
It affects any enemy formation assaulting or assaulted by the formation with Nurgle's Rot
It affects any enemy formation assaulting or assaulted by one or more formations with Nurgle's Rot
Personally I think they shouldn't have the attached character, and should just be 4 scouting units acting forward on their own. Possibly with a small points reduction to 175.
Real life means that I'm not getting any batreps done, but I hope I can in the (hopefully not too distant) future.