Mearls and Crawford have been saying for months now that to them, math fixes were the easiest thing for them to do, so rather than worry about that through the early part of the playtest, they focused on the "shape" of mechanics (my phrasing). Do people like Advantage? Do they like the Skill Die? Do they feel like they have enough interesting things to do as a fighter? The Barbarian is a good example, as it came out incredibly imbalanced, and the design team said this was on purpose, because they could always scale back the numbers, but they wanted people to get a clear take on the class features.
Now, the counterargument is that it helps to get a feel for a mechanic if the math is right. But the question is, does that apply to everyone? And just how close does the math have to be? I suspect the take of Blackwarder's group is not uncommon. "Okay, the math is a bit out of whack here. Note it in the feedback and move on."
4e has some of the tightest math in D&D since Moldvay, particularly in comparison to 3e, so I think math is a highly salient feature for many 4e fans. And the common refrain I see is, "Why didn't they work out the math first, and then fit the mechanics around it?" I think they did to an extent with bounded accuracy. And they expected to tweak it as things went on. Here's the thing though -- 4e has real tight math, and people understandably love it. But there seems to be this tendency to believe that 4e had it's tight math worked out from the beginning, and I'm not sure there's support for that. The designer notes for 4e note when the team broke through on certain mechanics, but not on the math. Given that the game was released with monster math still a bit out of whack, and Skill Challenge math still a bit out of whack, I'm inclined to believe that on 4e, like on Next, much of the design was done using approximate math, and the math was further tweaked and refined late in the design stage, like on Next.
I suspect that when the finished game is released, we'll have much tighter math than we've seen through much of the playtest. But I also suspect that the tightness will fall somewhere between 3e and 4e. While 4e has shown there's a big market of people who want tight math, the success of 3.x and Pathfinder show that there's another significant market of people who don't need it quite so tight. I think there's a fear there that making the math too tight will turn some folks off. I don't think that's how it should be, but unfortunately WotC has to design as much to perception as to execution. 4e showed them that you could make the math tight, and give folks tools to adjust it, but that's not how some folks want to D&D.