ive have played against nurgle DL a couple of times and i cannot win. it depends on that he has higher WS is -1 to hit and has 5+ ward save.
what can i do against a nurgle army consisting of two units of plaguebearers twelve each. two units of plagueriders 3 each. och chariot och herald and one deamon prince.
my army is:
king and prince on foot and two liche priest on foot. 2*3 chariots, 20 skeleton warriors, 2 swarms, 3 carrions, tomb scorpion, 4 ushabti, 20 tomb guard, SSC
Get the charge with your TG, killing blow always kills on a 6, so you won't suffer from WS differences. The king should be able to kill the deamon prince if you give him the right equipment and he gets the charge. Most important, certainly vs chaos, is that you make sure you won't gét charged.