With a army based around nurgle you want a army good at the counter attack, so lots and lots of plague marines that are tough as nails to bring down, and some lurking fast attacks to bring in the counter assualtor just a helluva lot of marked marines and plague marines to lay down a good amount of fire while taking rough punishment
While its more death guard tactics, well death guard imo defines nurgle, so aim for alot of supression fire to cover your men for a counter attack against any assualts