Agree MW. It does appear to be a poorly depicted chart which looks like it could contribute to a crew initially interpreting descent point from 2500 at 10 dme. The Jepps chart for this approach that I have seems to depict the 3 degree constant descent profile much more clearly. The Jepps chart also has a dme vs alt table for the constant descent profile which helps with profile and support calls.
In any incident there are obviously a number of contributing factors but the chart depicted in the ATSB report is somewhat lacking in my opinion. Possibly a case of 3 degrees flight path angle selected at 10 dme, an error which went unnoticed for a while? There is mention of a new chart issued after these events, I wonder what the changes were?