Member formula in Stat account impacts performance

Summary:

I have a member formula for calculating DSI and the performance is bad when this account is retrieved in SmartView.

Content (required):

This formula takes around 10 min to retrieve in SmartView when Top IC member is used in POV. It works fine when retrieved at No Intercompany. I tried to use substitution variable to get the prior year instead of MDSHIFT, but it creates a problem when I retrieve values from historic years. I also tried using @PRIOR with including Year dimension, but that too didn't work.

Could you please suggest a better way to achieve this?

Thanks in advance,