If you want to work out ratings based on this years Home & Away, you could possibly think about this: Take a team's winning % and add it to their for & against % and then divide by two to get an average score. This should then give you some indication of the points differences between the teams.

In this case, it would be:
105.0 Brisbane
104.9 Port Adel
100.3 St Kilda
94.1 Geelong
87.8 Melbourne
83.2 Sydney
81.4 West Coast
78.5 Essendon
75.3 Fremantle
72.9 Kangaroos
66.0 Adelaide
63.8 Collingwood
63.6 Carlton
51.2 W.Bulldogs
44.2 Hawthorn
43.7 Richmond

That's not counting the Finals series though. If you did that, of course Port would be ahead of Brisbane.