That 4th line is on the high side for goalscoring, generally I don't think you should expect more than 30 goals out of your 4th line and based on Granlund and Chiasson's goal totals last season, you are already in excess of that marker. There are mitigating factors such as role where you might expect those two to score less, but then not accounting for Haas's production at all which should help bridge much of that gap.
I'll agree though that I'd expect much less than average 3rd line offense out of that Cave line.