I'd like to add my personal experience as of a week ago in regards to illusions: I bought all of them for 10 silver being the highest bidder. They sell for 2-4k each usually, but it's a very slow market with little interest. They might be a nice addition to your portfolio if you can get the mats with little effort, otherwise it's not enough to warrant investing in it. At least on my server.
Each of those modes existed long before this latest expansion; raiding is a basic concept in MMOs, and Mythic+ was added in World of Warcraft’s last expansion. The problems with Battle for Azeroth’s endgame come from the systems it adds, which most often artificially gate progress where most of the fun can be found. If raids and Mythic+ are the carrot, we’re about to talk about the stick.
Do you know members of the opposing faction in WoW clearly? In order to help all of us understand it, a potion is introduced in WoW's latest hotfix. Follow raiditem.com to know the details and think about why we should put down our giant axes and massive shoulder pads and give Sylvanas a timeout. Buy WoW gold at Raiditem and you can continue to enjoy big discounts we prepare for you during Christmas holiday.
Next, Enormous amount of mats? 4200 Ghost Iron Ore. That's it. Look at Depleted Kyparium Rocket or Turbo-charged Flying machine or the mechanohog, all have more complex recipes with mats requiring you to go to a vendor to get. Let's be honest I bought a bunch of Hula dolls because who wants to go to Shattrath anyway but c'mon. What you're saying is just not true. Its simple, its quick, and the procs aren't random (I transmuted 100 Trillium bars last night and got 122 bars). Most people don't need the procs, but optimizing allows you to make more gold, and ultimately this is a goldmaking subreddit. If you don't want to follow the advice, don't join that market.
You will get the recipes for these high level armors through a new discovery system. First you have to craft the base ilvl 355 armor (normal raid ilvl) which requires BfA Leatherworking 115. After you craft this armor, you will discover a new recipe, which is ilvl 370 (heroic raid ilvl), and after you craft one from the ilvl 370 armor, you will discover a new recipe for an ilvl 385 armor (mythic raid ilvl).
WOTLK and Cata were my goblin training grounds as well (I remember fondly making 30k on a single day after a patch day with Inscription), but since Im only at Legion levels, Im struggling to find oportunities where to start invest and make profit. I've been carefully paying attention to the market and picking small batches of mats to flip. After 6 yrs out im slowly starting to pick up (so far i think i made 100k in a couple of months).
There's a few profession crafted pets in BfA on the horizon - Battle for Azeroth Tailoring is getting a Hot Air Balloon style pet, and BfA Alchemy looks to be getting a brand new Transmute Meat to Pet. There are some mount buff consumables from both BfA Leatherworking in the form of a mount barding, and Blacksmithing in Battle for Azeroth will be able to craft Stirrups and Hoofplates to increase mount speed and allow you to interact with things while mounted.