I will amend my statement slightly: A loss by a Tier 1 team to a Tier 3 team should be a shock (witness SMC's loss to USD last year). SCU losing to a Tier 3 school would not be a shock.
Also, USF and SCU were both Tier 2 schools last year, so GU losing to them is not a shock. I consider GU and SMC to be the lone Tier 1 schools last year.
Maybe we just have different ideas of Tier 1, 2, 3 (4, 5, whatever....)