Interesting press release from Pirelli. I have to think they should have known about this going on but when they're unable to test their tyres on up-to-date cars it must be difficult for them to assess the risks of "off-label" use of their tyres.
As someone above said, this is common in F1, its a part of F1, making tyres where STANDARD usage in F1 is "off-label" points 100% to designing tyres for the wrong use, so the fault is with Pirelli completely.
I think people are making too much about the specific tyre and who will do well on them.
Merc aren't getting heat into a specific tyre and other tyres its worse. Its getting heat into tyres because by car design its heating up the rear tyres more than other cars, thats the same on a hard, medium, soft, inter or wet, it just runs tyres a bit hotter. The harder the tyre choice the better they'll last, they'll still have inferior tyre wear to those that heat up the tyres less(in most cases). Switching the tyres won't help Merc(directly), it will move the entire field, if the tyres run a little cooler, thats the same for everyone. If tyre X currently lasts 15 laps on a Merc it will run 20 on a Lotus, if the next lot of tyres run for 20 laps on a merc, they'll run for 25 laps on the Lotus.
The changing tracks are effecting tyre performance, because at one race the lets say the Lotus can run 30 laps on hard, 20 laps on medium and the race is 49 laps, so its perfect. Another track they'll do the same but the race is 60 laps, so they have to make a second stop.
Now the same two tracks lets same Merc can do 18 and 25 laps, that first 49 lap race 18+25+25, it has to do 2 stops to Lotus's one stop... boo, in the next race the Merc STILL only does 2 stops, and now Lotus have lost the advantage.(I was using changing laps to make it easier to understand, in reality we have changing lap numbers and changing tyre conditions at different tracks).
Some races are going to line up for a perfect strategy for certain cars, other races it will be just the wrong side of tyre wear and will be disadvantaged.
Merc haven't fixed their tyre wear, the same way they won at Monaco then went backwards in the next races. its likely improved, but the british GP was dictated by everyone scared of exploding tyres, not the pace any of the cars were truly capable of. Merc have been upfront and held position with heavier cars finding it harder and riskier to pass but only in the first stint, after that they've almost always gone backwards(sometimes earlier as well). This weekend after the first stint everyone was in tyre protection mode, with two safety cars and a lot of luck Rosberg got the win, its literally impossible to say who would have won without the tyre blow ups and Vettel's failure.
They were the third best car, at best, in the previous race in which they also started upfront, I have no reason to believe that has changed as yet.
New tyres will help and hurt ALL teams at some stage for the rest of the season. In fact it could just as easily increase the number of races in which Lotus can do less stops than others, as increase the number of races in which Merc hold on for more points.
Merc's young(not young) driver test loss could have a significant impact on the rest of the season, everyone is getting a 3 day(iirc?) test in which to improve and test parts that Merc haven't and won't get.
I do think their overall tyre wear will improve throughout the season as I would guess the vast majority of focus on the 2013 car and then inseason development was on tyre wear. I just doubt they'll "fix" that problem completely. That car is fast though and Hamilton on older tyres was crazy impressive in that final stint vs Alonso/Webber considering the older tyres both hanging on to then gaining on Alonso was amazing.