I miss the mobile auction house. I was disappointed when they retired the WoW app in favor of the weird mini game ones. I would use that quite frequently in my attempts to acquire in-game wealth. Usually selling raw mats in bulk.
I've tried the Bracers technique for Expulsom, by my luck seems way too bad. Best case scenario I get 1 expulsom every 10+ bracers scarapped, it seriously made a dent in my economy :/
I tend to use Undermine Journal a lot of as an outside source of gaining gold prices (usually its up to date but sometimes it might be 1 hour for the last update). I wish I could make a program or website that can pick up current prices of items on the AH so I can resell for profit by having it ping me the moment something hits a threshold of some sort.
For outside gold maker uses, I use allot of youtube videos and suggested online guides. If I could make a gold app, it would be to calculate information in game to more simple terms to save time and help new players understand the economy.
The problem is for the people that didn't manage to do those high gold missions back in WoD or those that are newcomers into the game have to grind everything with multiple characters in order to keep up. So having them back would be beneficial.
I don't necessarily miss having to log into so many characters to check/send missions, but I do miss the easy gold. If it was worth it for gold-making to have to log in 10 characters I would probably do it (depending on the amount of gold we're talking about), but anything beyond that is probably too much for me to do every day or even multiple times a day.
If it was possible to farm money by doing mission (just like in WoD), I would do it, but currently I don't think it's effective enough.
I missed the missions from legion, they gave me a way to sustain consumables as a guildless raider, now that there isn't a steady way of making gold, I can no longer justify buying flasks for PUGging.