As a scribe, I often have upwards of 200 auctions going at one time, just in glyphs. My situation is that I put all my glyphs up before I leave for work, then come home 9 hours later with the majority of my auctions being undercut, with 3 hours left. Instead of waiting for the time to run out, I'd like to see a way where I can cancel all unsold/unbid auctions.
If there were a checkbox next to all auctions so that they can be "selected", you could choose multiple at a time. Say, you could have a "Select All" and "Select None" button, or select them individually in your auction list. When you're done selecting you can hit the "Cancel all selected" button, and have a single confirmation box pop up reminding you that you lose your deposit fees, etc.
To go even further though, another option would be to add an "extend auction" option, where you can extend the auction by 12 or 24 hours, up to 48 hours, and you are charged the appropriate deposit fee. This way, you could totally avoid your auction times running out, but you couldn't adjust the price to repost. This feature wouldn't be as useful for items that have high competition, but would be for rarer items that you'd keep reposting at the same price.
Just a couple thoughts to try to make auctioneering a little simpler.