This is the UAC ATAR profile for this January round of offers
https://www.uac.edu.au/assets/documents/atar/ATAR-profiles-Jan_Rd1-2018-19.pdf
It shows the statistics of all the UAC offers on January 11th including Griffith Dentistry.
The documents shows <5 (so obviously 4 or less) got an offer through UAC which means that the huge majority of people who will get an offer ONLY applied to QTAC.
Since we already have 2 people on this thread, there's probably at most 2 more who got a Griffith dental offer through UAC.
Out of these 4 people, the lowest adjusted ATAR was 99.8!!! (this may or may not necessarily be the cutoff for QTAC since it's the lowest score amongst the 4 successful people on UAC. )
nirav and mzho got a GPA of 7 (which should equate to 99.95) so it's not one of them.
Assuming 6.5 = 99.00 and 7.0 = 99.95, an ATAR of 99.8 should equate to 6.88 (which will more than likely be 6.875 rounded up).
So while a sample size of 4 or less is too small to conclude conclusively, I think it can be somewhat deduced that a GPA of 6.875 is perhaps safe for entry??? We'll have to wait and see...