There is a known performance problem with Talend SCDs , not just with Vectorwise.
Rather than caching the inserts and updates and then performing them at the end of the process using a single ODBC connection, the code that Talend generates creates a JDBC call for each insert and update. This may result in substantially slower performance of the SCD processing.
Performance may be improved by creating self designed SCD components.
There was a ticket opened with Talend [#TDI-21040] Performance issues with Talend Ingres SCD component - Talend Open Integration Solution
to investigate the performance , feel free to update it.
As for the memory problems , what OS version are you running ?