I haven't done Perth to Broome but did Perth up along coast to Exmouth then across to Tom Price and Karinjini National Park then back down inland route to Perth that was back in 2005. Mum and Dad have just done Darwin to Melbourne via Broome and Perth. I didn't think any of our trip (pre kids) felt particularly isolated to be honest - a long way between petrol stops at times though. I suppose depends what you mean by isolated.