Sounds good. Well, let us know how things do.
Any reason you're not including any plague marines? Also, why a squad of cultists instead of a third unit of pox walkers?
I have grown to dislike proxies in 40k. I feel like 'if you don't own it or want to spend the time to do your best to convert it, and it already has a model. Then you shouldn't be able to use it'
While I had no problem with my cultists being Plague Zombies in previous editions. Currently we have Poxwalker models thus Cultists will be Cultists in my lists. I only own this many Poxwalkers currently but yes ideally i would prefer more poxwalkers for this type of list.
I love plague marines have had great success with them, but they just wouldn't fit points wise into what I want to run. With cult marines I like to strongly adhere to sacred numbers so a unit of 5 is out of the question. Papa Nurgle disapproves of such.