Also do UNCHECK the Option "Multiple SQL Statements for each measure" in IDT, assuming your universe designer has checked and resolved any fan/chasm traps in the universe.
In your scenario this will lead to just ONE, effective SQL code being generated in Webi along the lines of:
SELECT SomeDimensions,
SUM (SomeMeasure), Count (SomeDimension)
FROM FactTable_1, DimensionTables
...
GROUP BY SomeDimensions