Speaking as someone who LIVES and invests heavily in the area, I can tell you that yes, there are a lot of people on low incomes, however there are also a lot on high incomes too. Someone on a low income does not make them a bad tenant.
One of my best tenants is a woman on welfare and her adult daughter. I think they have been living in one of my properties for around eight years now. Rent is always paid and the place is spotless.
Then there is the family that rent two of my properties. The mother and grandfather live in the house at the front, while the son and his young family live in the house at the back. Next door the daughter rents an old housing commission place from someone else. The daughter's family are on a large income, but prefer to live in this area (saving for their own home) because it's cheaper. The rest of the family have moved to be close at hand.
I would never suggest to anyone to buy a place sight unseen, but I wouldn't advise someone to do that regardless of whether it is in Western Sydney or anywhere else. If someone is interested in purchasing in the area, and are not prepared to come and check it out themselves, I would suggest they use the services of a buyers agent. There are plenty of reputable ones about.
There are a small component that have social problems. However you find this in many other areas too. Like I said previously, I have invested in more than one area. I have had good and bad tenants in more than one area.
Mt Druitt has been a lot less problematic than my quiet regional area that I hold properties in, and they are not even in the "bad" area of town.
As an aside, my kids, having both grown up in the Mt Druitt area came with us to Granville (MIL lives near there) one day. We were walking up the street and one of them (I can't remember which one it was) said that she didn't like the area at all and was scared and could we please hurry back to the car. Neither one of them has ever said that about Mt Druitt.