For IAD, an hour wait is NOT an anamoly, but SOP IME ... it's why I so rarely check luggage when returning to Dulles. I usually assume it'll be minimum 60 minutes extra for the "privilege". Late night flights are especially horrible as they have so few baggage folks out on the ramp, they unload multiple flights and bring the bags over together.

The international luggage dump seems to be the best, probably since those areas only have so much capacity and CBP wants to keep people moving along.