Foxy_Dread answering my own question about 1 extra point for 8 extra goals, I think the following explains it.
Last season the defence suffered more against the better teams, the lesser teams still weren't opening us up. This season the defence can be exposed against any class of opposition, so in the games where we are likely to score goals we need to score more goals to get a result. 4 to beat Bournemouth and Fulham, three to beat a poor West Ham and Southampton.
An attempt to look at this as a neutral. I think the above makes sense and explains why more goals does not bring the points you would expect.
Now the angled bit. Does this mean that our defence is more of a hindrance this season than last. By defence I don't mean the four defenders, I mean the team defending as a whole.