The story of 8.3 is overshadowed by the cloak, the story is build around the cloak making the story itself dull and meaningless.
Think this article is longer than the "story" of 8.3, most of the new content is flying from a -> b...
Garrosh tries to kill Anduin and leaves him for dead, before Wrathion helps him. And Wrathion's actions inadvertently and indirectly lead to Varian dying. Maybe he's mad at him, but doesn't want to be. There's a lot he could be angry about (all the other people dying from the Legion's invasion, for example) but the thing he chooses is the thing he can forgive him for because of how little it's Wrathion's fault. Or maybe I'm reading too much URT into it.
Personally, I highly enjoyed this Patch 8.3 lore article! And thank you for all of the lore links and videos to watch! I'm not one ever looking for a "basic summary" when it comes to WoW lore, and this was a highly satisfying read. Especially since I was in Classic and suffering from boredom from fishing for Oily Blackmouth on a low level toon for hours (making gold). After reading this though, I came to the realization of how much the story behind this 8.3 patch release closely coincides with WoW Classic's Blackwing Lair Raid release (Phase 3) and the story behind that. The 2nd Legendary item, Lame-tonnerre, épée bénie du Cherchevent, became attainable and the most epic and beloved legendary at that when BWL was released. However, even in what we know as Retail WoW today it was a PITA to obtain, so it comes as no surprise that this 8.3 Legendary cloak requires months of farming certain criteria to make it into what it's final state will be before Shadowlands hits. AND, with all it's corruption influence, I could see the cloak being useful in the Shadowlands initially (at least briefly, like the Legion Artifact weapons did at the start of BFA).If one looks at the lore from Ragnaros, enslaved by the Old Gods, and Nefarian, Wrathion's brother, there sure are a lot of lore references in BFA Patch 8.3 that coincide with Classic and continue the story line leading to the source of corruption that began long, long before Wrathion was conceptualized (by us). I have yet to experience the story line in 8.3. I've stayed content playing in Classic after 8.3 dropped, completely avoiding all the auction house and mail issues that have created a "sh*t show, obviously". :D