I can tell you that there are very few auction house "bots" now. Many people do run auctioneer which has a manual scanning feature. Considering it's one of the most downloaded addons its not surprising your stuff gets purchased soon. You can't really compare BC to now, security has changed a bit. If you just type in what your posting in your buying toon, post it search and purchase one at a time you really shouldnt have any problems. I check @ STV and purchase from Winterspring, most people wont go to tanaris for a shared AH. You can also try and open trade with people if they are on your same faction, this will let you know if they are opened on the auction house or not since it will deny your trade attempt.

To minimize gold spent on deposits and taxes lost, I try to move enchanting mats for stuff I need, or pets and stuff so there is minimal deposit and tax.