There are a lot of things going on right now in Blizzard development. The big files we are currently downloading, aren't just additions to wow that will likely double the size of you install, the majority are just updates that will over write current files.

IE, new talents, new glyph changes, new UI changes, ect. I am willing to bet that a lot of what blizzard is uploading to us right now, involves the cataclysm world changes, and is the reason why the data is so big, and we are downloading it in spurts, rather than all at once.

Several blue posts talk about how the people in the office are currently working 7 days a week to try and piece everything together for cataclysm, ensuring that we have a good product that can stand on its own merits, giving us something to enjoy for the next year.

Now, I understand that 'X numbers' are a problem right now on the PTR. However, numbers are usually the last thing to get a pass through Development, as you want your game mechanics polished before you start tweaking coefficients or damage/threat numbers.

As I said before, don't even bother logging into the PTR to check the numbers, many classes are OP, some are mediocre, and some are just plain terrible right now. Dungeons and raids aren't going to be very fun on the PTR, simply because for the most part, professions that enhance your performace have changed, are largely unavailable due to lack of a proper AH and broken UIs, so players cannot optimize characters that copied over with the wrong gems/enchants.

Right now the focus is supposed to be interface bugs with the new systems, IE, talents, glyphs, character sheet, action bars, abilities, ect. Blizzard wants to make sure those things are working correctly before they start looking at numbers and making adjustments.