I don't think the formation is the big issue. Aberdeen and Rangers were both totally reliant on the number 9 scoring and when that dried up they went downhill.
We were sharing the goals around but without any regular scorer you are always likely to regress. We needed a centre forward who could score AND Scott to kick on and we went on to sell Scott and brought in Ndjoli and Watt.
Robinson hasn't signed a regular scorer in five transfer windows. It's a glaring flaw.