Just to cover the entire ground:
Currently:
- Wins: LH 9, NR 9
- 2nd places: LH 3, NR 4
- 3rd places: LH 4, NR 2
This to me highlights it pretty clear if there is a tie in points:
- Whoever wins AD has one win more
- If LH gets a 2nd, he ties NR for 2nds, but then has more 3rd places
Thus.......
Rosberg is champion when:
- Rosberg finishes on the podium regardless what Hamilton does
- Rosberg finishes 4th, Hamilton must be no better than 2nd.
- Rosberg finishes 5th, Hamilton must be no better than 2nd.
- Rosberg finishes 6th, Hamilton must be no better than 2nd.
- Rosberg finishes 7th, Hamilton must be no better than 3rd (2nd ties them on points and 2nd places, but LH wins by more 3rd places)
- Rosberg finishes 8th, Hamilton must be no better than 3rd.
- Rosberg finishes 9th, Hamilton must be no better than 4th.
- Rosberg finishes 10th, Hamilton must be no better than 4th.
- Rosberg finishes outside the points or DNFs, Hamilton must be no better than 4th (4th ties them, but Rosberg wins on 2nds)
- Hamilton finishes worse than 3rd (4th would tie them on points, but NR has more 2nd places)
Hamilton is champion when:
- Hamilton wins, Rosberg must be no better than 4th (4th ties them on points, Hamilton wins on more wins)
- Hamilton finishes 2nd, Rosberg must be no better than 7th (ties them on points, Hamilton wins on more 3rds)
- Hamilton finishes 3rd, Rosberg must be no better than 9th
So which ever way you want to put it, Hamilton must finish on the podium to have any chance of securing his 4th WDC. Some other interesting points;
- NR finished lower than 3rd on four occasions (5 if you count the DNF in Barcelona) in 20 races so far.
- LH finished lower than 3rd on two occasions (4 if you count the DNF in Barcelona and Malaysia).
- If LH didn't have the DNF in Malaysia, NR would have finished lower than 3rd on five occasions
- NR finished 4th in Austria, arguably of his own doing by coming together with LH.
- There is a high probability the Mercedes would have finished on the podium every single time if not for either a technical issue or crash or DNF (except I'm not sure NR in Germany where he finished 4th... was it a bad start?)
EDIT: Edited english...