First, the workaround is fortunately not to simply manually post all your auctions. When you have 300+ glyphs (for example) and dozens of types of cut gems that you probably want to be listing for all the new demand that 4.0.1 will generate, sitting there with the default posting interface does not cut it. It doesn't show you the similar auctions you will be competing with in the same frame, and it doesn't suggest a remotely intelligent default price.
That said, to fix QA3 (only, for now), simply download and install this addon. [edit: credit where credit's due. This was written by the awesome folks who spend their days at the JMTC forums, specifically Zerotorescue, the author of the QA-poster addon]. Without it, QA3 will just hang. With it, you're presented with a handy-dandy little box saying, "Do you want to post this auction?" It doesn't seem to work with Auctioneer (currently, the box comes up but doesn't seem to work when you click it), but I have faith in the Auctioneer dev team's ability to get a new build out fairly soon when its product stops working. Still, gems and glyphs are expected to be the big sellers come patch day, and those are both markets that QA3 does very well.
Apparently, addons are still allowed to automatically price for you, and that's one of the two biggest advantages that QA3 gives us, in addition to automated batch selling and canceling. The only change is that you need to click once for every group of auctions. Luckily, you can still keybind the action of clicking the Yes button: Simply create a macro with this line in it.
It will work for canceling as well as posting. Drag the macro to a button, keybind that button, and you're set. This type of automation was covered in another article
: same principle, different application. It's not perfect, but at least it's better than using the default UI to post several hundred types of products by hand.
I am not going to hazard a guess about what drove the fine folks at the Blizzard UI dev team to make this undocumented change to the functions used by these addons specifically to service the glyph and gem markets, but it's a little rough that it's happening simultaneously with a patch that's expected to drive more demand for them than any other patch in the history of the game. Patch 4.0.1 is drastically changing the desirability of stats to many classes in the game, and a huge number of people will be regemming from armor penetration to something other than crit (which is what ArP gems will give you after the patch). Also, now that we can learn every glyph in the game, there's going be a huge surge in demand for glyphs as people scramble to get one of each.
Maximize your profits with more advice from Gold Capped, plus the author's Call to Auction podcast. Do you have questions about selling, reselling and building your financial empire on the auction house? Basil is now taking questions for a special series, "Ask an auctioneer," at firstname.lastname@example.org.