When cars have similar lap times they can hold position. The overtaking after the first stint was partly DRS but mostly tyre wear. I mean did you see the way massa caught rosberg up through turn 8 he would have nailed him with or without DRS because he had a massive grip advantage coming out of the turn 9/10 chicane.
Also the Alonso - Webber battle was great because Alonso made a good move early on to get past Webber but as the strategy played out and the fuel loads came down the maximum pace of the cars changed and Webber was able to retake his 2nd position.
What the DRS does do is stop the drivers from attempting marginal moves and taking themselves or competitors out because they know that if they concentrate and put in good laps they can overtake at some other point in the race. There have been 0 safety cars so far this season and very very few 1st lap collisions so the racing is defiantly at a higher standard.
I do think the DRS zone in Turkey was a touch too long though but it is something that the FIA will get to grips with so they can more accurately judge the length of the zone to make overtaking possible without being too easy if the car in front is of a similar pace.
Yes, the different tires and the requirements to use both are also an attempt to manufacture passing.
Soon, they will figure out why passing is difficult, and then maybe we will finally get back to the wide open F1 we had before, with different cars, different engines, and different tire mfgs.
Then we will have proper passing. Then we will have cars come from the back by passing all the other cars on the track.
The intent was to save money, but that hasn't really happened, so there's no need to continue down the path of making the cars the same, imo. The teams with the money remain at the top of the heap, as usual.
Why not just call it "Push To Pass" like Indy car does? Next year the button will get you an extra 100 horses, just in case there was any doubt about the pass...