That is too bad... I thought they had told us in 10.1 they would follow the "normal" BW architecture which would imply partitions are possible. Interesting that you only have 13 dims and your performance is still bad, I just assumed ours was attributable to having >13. We have some models with 15 dimensions and 100M+ rows and the performance is TERRIBLE. We are getting ready for a go live so I haven't had much time to dig in. I'll let you know if I find quick wins.
-Mark