Try testing with this preference RAC_expand_below_batch_size to different values. By default its set to 1000. What it means is it expand the BOM in a batch size of 1000 lines. Setting it to -1 means the entire BOM gets expanded at one shot. Depending on the size of your workstation and network speed you can increase this value. It usually gives a good result, especially if the client is over WAN.
NX 11.0.1.mp01 | SW 2016 | TcUA 11.2.3
Another option I can think of is to udnerstand if there is anything that can be optimized st the DBA level. You can check with your DBA to check the queries from your session or run AWR reports to see if there are any queries that can be optimized for performance.