Every single time I've heard the lines "Bring back player trading" and "We need the AH back" all I hear is "Please let us bot on a second/third account, and buy gold from 3rd party websites."
Trading would do nothing to increase the overall chances to get loot. It'd still need to drop for someone, and the only way to increase that number is to bring more players in. The only way to bring more players in to farm loot is to bot, or have an asian army bot for you if you want to see a decent amount of the rarer items enter the system for you to AH. .. oh, and just want currency are you going to use to buy those items? real life cash from 3rd party options, or with in-game gold for hundreds of billions?
Please, refrain from stating that you'd just need to hit that one lucky item to sell for trillions so you can buy that item for trillions, or you know, fork out some cash on the black market.
There NEEDS to be rare items, and while I agree that knowing there's RNG piled on RNG + a little more RNG making it extremely unlikely, makes it feel like it's a little more like winning the lottery and thus why bother? KNOWING what the percentage chance is, doesn't change anything. We all knew that items like Unity, T&T, set gear was rarer that other gear... and we still played because it was fun, and that chance to get the gear to play the build we saw on youtube and thought, shit, I wanna be that guy.
We already have target farming via gambling, sure, it's not as narrow as some would like, but it IS in the game. If Unity had a higher chance to drop from Azmodan, then EVERYONE would be killing Azmodan over, and over, and over again and wouldn't even bother to touch a Rift.
I like the fact that I can kill anything, anywhere and have the same chance to drop a Unity.