Ott
For 99.9% of property transactions in WA a settlement agent is all you will ever need.
The problems only arise when there are significant problems with title, caveats or rights of way etc etc, in which case the settlement agency should advise you to get a solicitor involved if it is outside their area of specialty.
Personally I have never needed this and am more than satisfied using a competent settlement agent.
Rgds
Joe D