Holden Commodore: Tyre wear on VE

Since fitting four new Bridgestone tyres to my VE Commodore earlier in the year I have travelled 15,000 km, mostly on the highway with cruise control. The front tyres are fine, but the rear tyres now need replacing as they are down to the indicator. The tyre company where I bought the tyres told me that this is a common problem with the VE. Yet my mechanic said he has never heard of this, but did however hear about cheap and nasty tyres being imported and labelled as brand name tyres. Any further insight you may be able to provide would be appreciated.