Went up against a nurgle marines/demons combo that just kicked my ass, was wondering if you guys had any tips on fighting against nurgle as crons. His army, as far as I could tell (don't know much about chaos armies) was a demon prince of nurgle, havoc squad (mark of nurgle) squad of plague marines in a land raider, 20-ish plague marines with typhus attached, and epidemus with a couple other demon units I did not recognize that sat near him.
The problem was that everything I threw at him he had some just absurd
fnp/cover save ALL. THE. TIME. My squad of tesla carbine immortals did the most work, and that was thanks to the two lords in the squad convincing the demon prince/land raider plagues to punch themselves in the face, they got the only significant kills on my side that game. Other than that, the typhus blob has some invisibility

and shrugged off round after round of doomsday, massed gauss (rapid fire after a certain point), and my tau ally's (we were running 2v1, 1000+1000 v 2000) crisis teams, fire warriors, devilfish, and sniper drones until it hit our front line and cut through it like so much wet tissue paper.
Any suggestions?