Soloing an instance can be all the more profitable if your character is an enchanter. During any solo instance run, you'll end up with some items which can be sold or traded, and some that are bind-on-pickup. Non-enchanters can only sell these soulbound items to a vendor, but an enchanter can disenchant the bind-on-pickup rare items, and then sell the shard/dust/essence instead of just selling the blue item to a vendor. (A side benefit of selling enchanting materials is that they do not require a deposit to list in the auction house, allowing you to list endlessly until the item sells.)
New to Patch 8.1 is a new leveling flask called the Draught of Ten Lands which increases all primary and secondary stats by 20 and experience gained by 10%. This effect lasts for one hour and persists through death, similar to other battle flasks. This item can be purchased using a new Patch 8.1 currency called 7th Legion Service Medal or Honorbound Service Medal which can be earned doing the new incursions and Warfront activities. Simple earn these medals on your main character, purchase the flasks, and send them to your other characters. The cost is 10 of the medals.
5% was admittedly an exaggeration, just felt that low. I'd say it was probably closer to the 30-40% range. It was Artifacts of the Blacksilt, spent a good 10-15 minutes killing Blacksilt Seers to get two damn idols to drop. A quest that had me killing Elder Brown Bears for bear flanks also took quite a while, though that was less due to drop rate and more due to how spread out they were.
2. Once you have an interested buyer, stay firm in your price. This does not mean to never make them feel like they are getting a bargain. You can subtract 5% off the price and not be hurt as long as you still make a profit! Remember this, as that 5% may not be a big deal to you, but the buyer will feel special and might buy the item for the slightly reduced price. I can not emphasize enough that this is not the same as undercutting! Do not drop every good every time or you develop a reputation as a soft seller and people take more liberties in their dealings with you. If you give someone a constant 5% discount, then they begin to want 10% and then 15% until you no longer make a profit. Discounts are used when you feel that the seller may be pulling away and you really want to just profit and move on!
Majority of world quests provide pretty bad rewards. Running for a wq that rewards 130 gold is a waste. Resources are not that necessary apart of some rare profit missions or buying the seal for them. Azerite for non-raiders or nonmythics is pretty much useless to farm since every patch will lower their requirement, and aside from few occasions it brings not much of a value. Not to mention that island expeditions are probably easier/faster with rng chance for tmog or pets. So the only main reason to farm them is the reputation. The most important is getting to exalted for recipes but for that there is no cache. The rest is pretty much not needed.
First of all, the value of transmog is decided by rarity and how they look. Some items like Minenarbeithut der Tiefen or Pendel der Verdammnis (they can drop in Uldaman) are worth millions of gold. They are worth so much, because they have a really small chance to drop. Other items are bought well because they look good. Best example in this case is the Glorious set, its legplates Glorreichen Beinplatte reach a 100.000 Gold value easily.