Hard to tell without selectivity / row count info, as Chris noted.

But, if the partition and dataareaid are how you typically query this table, and guessing that PARTITION is more selective than DATAAREAID, I suggest trying this:
Cluster the table on:
(PARTITION, DATAAREAID, DATASOURCE)
Make DATAAREAID [var]char rather than n[var]char if you can.  If it's not nchar, it's critical to get rid of the N'.

In fact, it's best just to get rid of it anyway.  If it's a unicode string, SQL will convert it to unicode:

(((PARTITION = 5637144576) AND (DATAAREAID = N'dat'))  ...