Thank you for your comment. It gives me an opportunity to explain missed parts.
My goals was:
1. Provide necessary monthly counts (measures).
2. Be able to present detailed records (consider my Comments field as number of joins to tables providing payment, demographic and so on).
3. Minimize ETL related objects (tables and scripts).
Count(distinct *) was an initial solution but as any aggregate it brings difficulty to provide detail records.
As for DW - Excel pivot tables are one of the way to present a multidimensional structures.
So all I need for virtual DW to prepare dimension tables and source to count measures.
Main problem on my way were the duplicates and monthly granularity.
I concentrated in my article on this task for simplicity but seems it makes it vague.