To be honest, there must be more to these stories than just faulty Apple Map directions.
1. Mildura is well known as being a regional centre, and on the river. I find it hard to believe anyone choosing to go there wouldn't at least know that. So clearly, it's not going to be along a dirt road in the middle of nowhere.
2. Being the regional centre it is, the highways there are well signposted, with lots of directions pointing to Mildura, no matter where you're coming from.
3. Compare the difference in the route Apple Maps takes to the wrong location from Melbourne, and the actual route. The wrong turn happens in the town of Ouyen, where Apple Maps has you turning left on the B12 instead of continuing straight on the A79. Now about 100m before that intersection is a sign *clearly* indicating Mildura is straight ahead.
Surely, Apple still has some obvious things that need fixing in Maps, but there must be other things at play here.