I'm not in favour of the double points system because it is unnecessary and doesn't achieve what its designed to (overcome domination), but I find your view illogical/extreme.
It seems to paper over the obvious cracks that it is a very unequal championship in the first place, the cars are not the same, there are mechanical failures, some drivers benefit from no1 status, some don't. Etc.
It stands to reason that the pressure on a final race with the championship on the line would be harder to win.
Its no different than the fact the differential between 1st and 2nd is greater than 2nd to 3rd.
Like I said, my issue is its pointless and tacky. But if it goes ahead I don't think the sporting integrity is undermined at all. If you look at the bigger picture.
First of all it's a team sport, and as far as I'm concerned the WDC is a teams contest just as much as the WCC. The driver is just a member of the team like any other - the only difference with the WDC as opposed to the WCC is, if you want to win it, it requires you to focus on one driver and to maximise his points. As soon as you start to view the WDC as a contest between drivers, the object of which is to identify the best driver on the grid, of course you are correct that it is a joke, for the reasons you mentioned. But I don't think any of that impinges on the integrity of the competition, it's just a fact about the nature of the competition that it's about the man and the machine, and the preparation and servicing of the machine and the team operations etc, it's not just about the man alone.
In terms of the points system, of course various different points systems are possible, including systems with dropped scores, systems that reward consistently finishing on the podium above inconsistently winning, systems that do the opposite. The points systems that F1 has used in the past have generally had legitimate aims, though. The dropped scores systems of the 80s were intended to reward outright speed over perfect reliability. The change from 9 to 10 points for a win was designed to make winning pay. The subsequent changes have been designed to take account of improved reliability and to thereby make it possible for smaller teams to score points again, and also to reflect the fact that the manufacturers are selling themselves on the reliability of their cars and want to see reliability rewarded by the points system.
In my view these are all legitimate aims of a points system. As a driver or as a team you can adjust your approach to races depending on that system. For example Button and Brawn, having built up a huge lead in the WDC in 2009, knew that the most important thing for them to do was to avoid non-scores, and were able to see out the title by being consistent and scoring points in every race bar one. If the points system had been 10-6-4-3-2-1 they would have needed to take more risks to try to finish further up otherwise they would have been overtaken by Vettel. These factors are the same for everyone.
But with double points, how can you approach the races differently to account for that? Will the drivers be trying less hard in the non-double-points races? Will it be easier to win the non-double-points races? No, of course not. The system doesn't have a legitimate aim, it's a cynical idea aimed at manipulating things so the championship stays alive longer, and it will mean points are awarded on a randomly unfair basis. Whoever wins in Melbourne deserves the same reward as whoever wins in Abu Dhabi, end of.
I don't buy the argument that it's harder to win in Abu Dhabi. It might be more pressure if, come Abu Dhabi, a driver is involved in a close battle for the title, but the pressure applies to the other guy as well, so if title rival A's performance is adversely affected by pressure, title rival B's performance will be affected as well and therefore it will be no harder for A to beat B than it would be if it was the first race of the season and neither of them were under such intense pressure.