JC Panthers: Instead of breaking them all down like I did with the golem, I'll just note that currently on my server the Orb of Mystery and the Living Steel combined cost 36,000g. All of the panthers, except the Onyx, sell for 32,000g. A loss of 4,000g/unit, not including the gems. Once we factor those in, at a mean value of ~200g/unit, the loss per Panther jumps to 8,000g.
Patch 5.3, like all new updates, is attracting a throng of returning players, many of which will be undergeared and willing to spend Gold to catch up with the rest. While the profits might not be as lucrative as with the new items, there may be less competition here. The key here is scanning the market for in-demand leveling gear and producing the right amount to avoid getting stuck with an unsellable stack of outdated items.
I think that's server dependant. I make a lot of Golems, but the price on my server is high enough that you could buy all the living steel and still make about 20K (almost 200kg on AH). Its just that you proc all the way up the chain. You proc 20% of your trillium, and then 20% of your living steel. SoH and Ghost Iron are such low effort farms, too. 20% of 180 Trillium Bars at 500g is 18k more profit, 20% of 150 Living Steel at 3500g is another 105kg. That's an extra 25k profit per Golem. If they stop selling stockpile them for the next expansion, they always boom with the price of herbs. And a consistent 20% proc rate is the opposite of RNG, its extra free stuff as a benefit to completing an extra quest (not to mention for new alchemists the investment of leveling Vanilla Alchemy). You're looking for some get rich quick scheme, where the real way to build wealth is patience and volume. No market is going to be viable because you want it to be. Only because you make it viable.
Mythic+ rewards will also go up by 30 item levels; however, during the first week of Season 2, rewards from end-of-run chests will be capped at Mythic 6 quality (item level 385), and the chest you open next week will contain Season 1 rewards if you do a Mythic+ run this week. (So, for example, if you do a Mythic 10 during the final week of Season 1, you’ll get a Season 1 item level 380 piece and 60 Residuum from your first Season 2 chest.)