Fair enough - I have just opened a new ticket with some detailed info. I'll update here if I get anything meaningful.
Just to pick your brain for one more second - the specific information I am getting from the VizPlan is
Reason For Stacked Column-Searches: Unsupported join condition (Non-field join condition): BINTONHEX(A.PARTNER_GUID) = B.PARTNER_NO
The two fields in question are both type VARBINARY(16), Colume Store Type RAW. So they're the same type, and I am aware that the SQL engine will perform dynamic type casting. In this case, that specific join condition should not need to be converted unless the SQL engine cannot join these data types?
Regards,
Justin