The fix is a change to InterSystems' products.  If your application handles XML as described, we can happily supply the correction as an Ad hoc product distribution.  Please contact the WRC to initiate this.  Thank you.

Caché buffers can offer performance improvement depending on the current state of system tuning, however as long as you are modifying data those updates need to be written to durable storage (disk) at some point.  The performance impact Pete mentions above comes into play when writing to disk.  For a good discussion of tuning Caché buffers I recommend Murray Oldfield's excellent post in his Performance series: Looking at Memory.