I can actually easily do act 3 by: 1) surviving by being quick with smoke screen (and using it
a lot because I have 49 discipline), and 2) as you guessed, high damage. Only act 3 champ that kill me A LOT are the fast hulking phasebeasts
But without resist, I have to realllly keep my eyes open for projectiles

. I cannot yet afford to have all my current stats AND all resist - too expensive!
Ive sold a few rares for 8 mil and my highest legendary sale was this belt that I sold for 3mil. As soon as gold comes in, I spend it right away on items, fearing that if I hoard gold for long, its going to really drop in value fast. So mostly I am carrying 2-3 mil in stash. Item that id call "Great" are sold for minimum 50 mil - to buy those you either need to save gold for a looong time, or hit the jackpot!
Yeah a months(?) ago, sellin unID items was a geat thing because both people with low gold
and high gold benefited. Also, being smart on AH, like you were, is also a good way to earn gold fast. I've bought things for 50k that I resold for over 500k
