How many rows are returned by this query? Do you have an approximate feel for same?
Based on the amount of "thinking" that Sybase needs to do, it might just be Sybase churning and churning.
Another thing to try:
In the Data Source definition, turn the joined tables into a SQL Statement by choosing the "Custom SQL" option. Take that SELECT statement and plug it into another query tool to see how long it takes before results start coming back.