The design will be fine they test this stuff to destruction, it be a manufacturing issue.
They will make a lot of these in a day, it only takes a couple of rogue shifts getting something wrong and you can have thousands in the wild.
Those things usually get tested by a robot which can never truly simulate real life usage. All it will do is prod the stick.
Maybe it's the way others are using them?
I've got two controllers and they're both fine (touch wood).
If it's down to how people are using them, then surely their would have been similar issues with previous controllers?
I had 3 PS3 controllers and yes the rubber tore apart at the edges (but it didn't peel) after years of use on two of them. The difference with the DS4 is that it started peeling within a couple of months and then the rubber pretty much split soon after the peeling issue cropped up.
Huge difference there with my PS3 controllers lasting several years before I had to replace the sticks by buying some off ebay for a few quid than ones on the DS4 lasting a month or two.