Thanks for raising this issue, Kruffzz.
I’m not able to comment on every issue you raised, but I’ll try to hit some highlights that reflect work we’re doing for the upcoming Wrath of the Lich King release.
First, you mentioned inefficient addons, and you’re definitely right that addons doing full scans are part of the problem.
The throttles we added during Burning Crusade helped, but an important point is that they apply equally to addons and the default UI, and that approach is somewhat problematic, since addons have different behavior characteristics than our native UI. It’s not a one-size-fits-all sort of situation.
With patch 3.4.0, we’ll be separating the throttles for addons and native UI so we can more directly target the behaviors that cause performance problems for other users. That will allow us to allow the native UI to be less impacted by misbehaving addons, and will mean that addon authors are incentivized to make their addons more efficient, since the throttle is also tracked per-account. The ability to throttle separately is going out in 3.4.0 builds this week, and we’ll adjust those throttles when we release the patch live to address the worst issues.
You also talked about the default UI and how its missing the ability to sort by buyout and by unit price. Since low-unit-price-buyouts are the most common player desire, it opens up scam opportunities with low-bid-price on high-buyout items being sorted to the top, and encourages the posting of single-item stacks, since bulk-rate-max-stacks sort lower than single stacks. Because of that we’re going to investigate adding better sort options to Classic’s default UI in an upcoming patch. It likely won’t be in for launch, but we’ll try to add it as soon as possible.
Sorry it took us so long to reply to this. Its been on our mind a while, but we’re juggling lots of important issues for Wrath, and I wanted to make sure I gave you the most complete answer I could.
Thanks again! 
