Hi Ann,
Fetching 2000 rows of data into the excel will surely lead to performance issue. Instead of getting all data together, perform aggregation in webi side and pass only necessary data set to dashboard. Why can't you use multiple connections and filters and drill to dataset as needed so that data fetching to dashboard at a particular point of time would be minimum. This is the best practice rather than fetching all data in excel first.
Refer below link to see a very good example of implementing BIWS with webi block and filter. As shown in example, first use a connection to fetch the prompt list and whenever a particular country is selected, fetch data for the selected country alone using another connection.
http://blog.davidg.com.au/2011/03/drill-down-in-xcelsius-using-bi.html
Regards,
Nikhil Joy