Just remember one thing - No mutations on the beast except for Doubles.
Outside of that from a tactical/strategic viewpoint I think you're making an error. Block, Guard, Tackle & Mighty Blow have no suitable replacements in the mutation section - and three of those four skills are key to making a Nurgle team that has a good shot.
You can get away without Mighty Blow and only a couple of Tackle players - but Block and Guard are essential in avoiding your team being overwhelmed.
This said - The #1 mutation you'll want is Foul Appearance - that's the only way you're going to survive Blocking wars.
Then you'll need Claw to give you some offense.
Dist Pres will shut down Throwing/Hand Off plays (But you don't need much more of it - Just stick it on Rotters after they get Foul App and Prehensile Tail)
A bit of Extra Arms - No more than 2 Pestigors with it is needed.
Two Heads for Pesitgors
Prehensile Tail on everyone once you have whatever else they might have wanted.
Tentacles is rubbish - unless you're taking Stat increases, in which case stick it on anything with ST5 - but you might end up taking it as roll #3 on a Nurgle Warrior because there's not much else that helps them.
But you're going to hate Wardancers and other Leaping/Strip Ball types. In fact you're going to hate playing against anything other than Vampires & Stunty teams.
I guess this is what you'd want - in order of picks.
Nurgle Warriors - Claw, Prehensile Tail, Tentacles...
2 Pestigors - Extra Arms, Foul Appearance, Two Heads, Prehensile Tail, Claw
2 Pestigors - Claw, Foul Appearance, Two Heads, Prehensile Tail
Rotters - Foul Appearance, Prehensile Tail, Dist Presense
Beast of Nurgle - Good luck on the Doubles
