Yeah, your 60 minute additions are more often used as flavor/aroma additions for IPAs. You either need to really bump up your cascade amount (it's IBU's are usually <7), or look for another bittering hop.
Something like, 0.75-1 oz of either Chinook, Columbus, Warrior, Centennial, etc. would compliment your cascade/willamette combo.
EDIT: just read you're doing 2.5 gallon batches....(so adjusted the hop oz.)