You are likely running into a limitation at the OLAP Server level and not WRS. The OLAP Server limits the number of tuples returned by default. The default number is 1000000. You can increase this number by using the following steps:
1. Log into SMC
2. Expand Server Manager>SASApp>SASApp - Logical OLAP Server.
3. Right click on SASApp - OLAP Server and select properties.
4. Go to the Options tab and click Advance Options.
5. On the performance tab, change the value for Maximum number of tuples in a set
Increasing this setting will allow more tuples to be returned. However, enabling the OLAP Server to return more tuples will require more resources and I suspect you may run into memory issues. If so, you can increase the memory of the OLAP Server using the MEMSIZE option.
When you encounter these types of errors, you may also want to take a look at your cube design and the cardinality of your dimensions. Please take a look at
http://support.sas.com/kb/19/765.html for documention on how you can calculate result set sizes and the impact cardinality can have.