This must be the first WoW beta for you. Well.. State of Beta is actually just fine it's actually quite well. Let me break down some facts for you and compare milestones.
1. Raid Testing - In prior betas raid testing was done in the last 4-5 weeks of beta before launch and didn't get fully tested. Most of the encounters continued to be hotfixed even after launch as the hard progression guild plowed through them right away. This beta cycle The encounters and mechanics of the bosses will be tested during beta, not each individual skill level (LFR, Normal, Heroic). So Considering how fast the encounters are better tested and tuned. It's not going to be very long.
2. Stuff is Missing - Challenge modes have been appearing now. Each patch here on out will be adding more. Itemization is just about done. Pet Battles will be enable within the next couple patches as well as possibly Jade Forest returning (I'm on the fence here due to possible lore spoilers). Not much else missing.
3. Ah It's Done... QA - A Gold Master doesn't have to be perfectly done. WHAT?! of course it does?! no it doesn't. none of the release discs you have now are! They are all 4-5 older than release day. Gold master only has to have a majority of code on it to install a large base, the rest is patched in on launch day. Every launch day we have a patch. Don't you remember? we all curse Blizzard for it! Actually producing the Discs don't take much time either because retail discs are pressed not burnt like your discs are home. Look at a CD or DVD under a microscope. you'll see a spiral coming from the center outward of dashes and dots (actual pits) or 1s and 0s that the laser reads. Your "burner" at home uses the laser to burn the same dashes and dots on an organic dye layer. So where it takes 6 mins or so for you to make a disc, it takes mere seconds or less to press a disc and silkscreen the label on it. We've seen the box art already, so I'm sure they have already had millions printed and ready to be filled. So yes.. time, but not as much as you'd imagine. Mass production... it's the future
4. Safe to say August is past us. I'm done speculating on dates exactly. If you have read ANY of my past posts you'd know why. but I will say I think Mid-Oct is too late to be looking at realistically just by looking at the hard evidence around us.