We have an outliner with several columns that uses XmNxrtGearwidthSizingPolicy XRTGEAR_SIZE_VARIABLE because we don't now the correct size of each column(dynamic data). Another issues that causes problems for us is that we don't have the complete label for a node before we actually need to create the node. These issues causes major performance issues when using the outliner widget.
we have logged XRT-2503 to address this in the future releases. Take a look at the attachment for details of the Bug logged.