I've bolded out a couple of things here:
She had one massive opportunity vs Zvonareva, and posted a very abject performance, that's not good for one of the biggest matches of your career. You have to remember Caroline was better than the vast majority of the field when she posted this set of results. It's like saying Serena could play 3 straight weeks going into every major, she's still post overall good results, but her results at grand slams would decline as a result.
The second is a key thing for me. I know they said this, but for me this was just words, a cover for her form falling off the cliff. It was said when she was in a slump, at no point have they ever actually tried peaking for grand slams, what did they actually change in terms of events she was playing?
Her grand slam results have nearly always been below her tour results (2009 maybe arguable), her best results ever over a year period was QF, R4, SF, SF. That's nothing outstanding for a player who won 5 Tier I's in 2 years.
No she has not underferformed at hard court slams and particularly the USO. with F, SF, SF in 2009-2011. If you take the betting odds at the start - she exceeded
or at worst equalled them. In 2009 she way surpassed expectations. 2010 - all the talk was Kim and Pova. They were expected to make the Final. All the experts said that. Noone picked Caro. And the booking odds those two had shortest odds no matter where you went. And as for 2011 where she lost in the 1st round at Cinci and Rogers Cup - you think she underperformed at USO compared to those tournaments before because she didn't beat Serena in the SF
In my book she exceeded all my expectations at USO. It's overall where she ends up compared to what the odds say and hence where she was expected to end up that is the basic definition of whether a player underferforms or not.
Of course if you want to talk about Wimbledon and RG- her slam results have not been good. But she doesn't do great on those surfaces in the other tournaments. Yeah she won Wimbledon 2009 befoe she was on the Radar and expected to do much at Wimbledon. And then she has a couple of 1st round losses at Eastbourne. I'll grant that betting odds say she should have made QF at those slams. But people would still have parrotted she underperforms at slams even if she'd reached QFs at hose slams. I'd rather her meet or exceed her expections at USO than just make QF at those slams where her odds say she should have made.
As for your other point that when team Caro said targetting slams as their priorty in 2012 - you state that was just words and they didn't do that - again I disagree. You can have your opinion but it is opinion and not fact. Just because they didn't have what you think their schedule should be to target slams doesn't prove they weren't doing that. For starters - she was mucking about with all her serves being 2nd serves on the clay court tournaments as an experiment that Piotr wanted to try. That for a start didn't seem to be taking those tournaments seriously enough and a disaster as far as I'm concerned. The whole mindset seemed to be not to worry about bad results at tournements. I am quite certain they took their eye off the ball at tournaments with the "priority is slams" view. As certain as you are with the opposite view that if they hadn't changed their schedule to what you personally think it should be - that they didn't mean what they were saying about targetting slams.