[Avodah] structure of shmoneh esrai

[M Cohen]

We know that the original structure of shmoneh esrai (before addition of
19th) is 3 praise + 12 request + 3 thanks.

I was always bothered by the seeming lack of structure/seder of the middle
12. 
Basically it seems like just a chulent of important ideas.

(I know the gemora gives reasons why some brochos are ordered as they are,
but not an overview that explains all the brochos or the grand structure)

I was listening to a tape from R Bulman z'l who mentioned agav that the 12
request are also structured in groups of 3.

3 for individuals spiritual needs (daas/teshuvah/slicha) + 
3 for individuals guf needs (geulah/refuah/parnassa) + 
3 for Klal Yisroel's spiritual needs (geulah/leaders for justice/leaders for
torah) +
3 for Klal Yisroel's guf needs (rebuild J'm/moshiach/shma koleinu)

He didn't mention a source for this - is this his own vort, or have pple
heard/seen this vort in earlier mforshim?

Mordechai Cohen