You are absolutely right, OLAP solution for 150ish records will be overkill and the best solution will be a local binding. Unfortunately, as I mentioned custom hierarchy declaration is not supported. We will consider it (further investigate the technical possibilities and road-blocks) for some of our future releases.
The your proof-of-concept demo (thanks for that as it shows one possible way to accomplish this task) uses multiple dimensions per axis. This is the reason why you got three row fields and of course the three "All" section. This is expected for our rendering as every field represents a slice of the cube and its "All" row shows the grand total value. The best way to achieve the look and feel of Excel Pivot Table is using custom hierarchy declaration, which as I mentioned currently is not supported.
Let me know if other questions arise.
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