I'd also like to echo that these are the initial numbers heading into a PTR. And from my recollection, though there are exceptions, Blizzard intentionally over shoots and then reels back. That has been their maxim historically for better or worse.
By employing extreme changes they generate more interest (if only superficial) to play test the 'thing'. Higher numbers of people play testing, potentially brings in more feedback, which in turn provides them with more data to decide where to go. If the changes were minor out of the gate I believe the interest to play whatever it is they're testing wanes. Philosophically speaking their take on modifying existing content might look egregious but I believe there's intent to get it right by generating buzz. Otherwise, yeah, they are in fact pissing into the wind and I hope they would invest their time more wisely.
This is all specious reasoning on my part. So please take it with a grain of salt.
TL:DR; Just bear in mind these changes are in the PTR precisely because they don't rightly know where the numbers should be. And that they are high most likely on purpose to get more people testing boundaries.