Your talking about USING and ABUSING the AH at the same time and they are two different things. Using the AH would entail me using the gold that i have earned from drops i will not use by selling them on the AH as well as gold drops for killing/breaking stuff to purchase gear. Abusing would entail for the most part buying and selling or commonly referred to playing the AH to me of course its a opinion .
If you want me to finish the game without ever using the AH I would easily be able to do it. There's a forum on Diablofans.com specially ment for trading like in the old fashioned Diablo games where you clicked on a player in a town and it would trade them. The AH just makes that easier