Is 18 Nurglings excessive?

I just noticed that whilst Nurglings got a points increase to 40 pts due to their new 5+ invul, the full 6 model squad still only 70 pts. At 4 wounds a base with infiltrators they're obviously amazing at screening and they're great in my list in particular because I have a lot of guns that I don't want my opponent to be able to charge. I've generally tried to take 3x squads of 3 for this reason, a bargain at 120 pts.

Three full squads would be 210 pts, is that too high for a unit that's almost entirely there for screening, with a small chance of being able to score the odd secondary?

I'm not sure whether to go for it or maybe take fewer but take an extra squad of Cultists, as at least they have some OC for actions and primaries.