With the general nature of cargo exported from China (e.g. computers, electricals, solar panels), I find it hard to believe that the aircraft would have been significantly overloaded based on the aircraft's useable volume.
Time will tell, but in my opinion the reason for this accident is far more likely to be due to the way the aircraft was hurriedly introduced into service with a carrier that was unfamiliar with the type and poor company SOP's allowed the holes of the swiss cheese to line up.