We also do MTBF analysis in ARW environments.
Although, I do not know your application it may not be the PI E that causing your numbers to be to high.
ANSI/VITA 51.1 introduces much more favorable quality (PI Q) factors for commercial components. Ceramic caps and chip resistors go from Q=10 to Q= .1, IC’s and semiconductor from Q=10 to Q=1. etc.
Our MIL/Aerospace customers accept these modifiers and have been told that they are going to incorporated in MIL-HDBK-217G if it’s ever released.