Rasha'nan taunt swap mechanic not working as intended?

Just got to try out mythic Rasha’nan for the first time last night as a BDK and the taunt swap mechanic seems easy enough to understand and execute but during every encounter there’s always something weird going on with how the threat decides to snap between Tanks. I was in communication with our other tank throughout the fight and they were saying the same thing.

I understand the idea is to swap mid cast during his first Savage Assault. That way when he casts his second one, it will be cast on whomever taunted. It does work a good majority of the time but there’s also a lot of times where either the taunt just doesn’t register, or the boss snaps back to the original tank causing them or you to get 2 stacks or even 3 somehow.

After deep diving into a summary from WipeFest and looking at the time stamps where the taunts were placed, it leads me to believe that the window of opportunity for taunting may not be working as intended. Sometimes it felt like the sweet spot was within 0.1 - 0.3 seconds of the cast, other times it felt like between 0.5 - 0.8 but we’re talking about two windows within 1 second! However, if you look at the actual spell on WoW Head, it is technically considered to be an instant cast spell. Even though he clearly has a cast bar… so how is this intended to work out from blizzard perspective?

I also watched Method, Liquid and other Tank PoV’s and it obviously happens to them too. It feels like either there’s an issue with threat snapping or, an unnecessarily misleading window of opportunity for the taunt swap to work. As long as you don’t taunt the boss AFTER the cast goes off, during his second cast, I feel like this mechanic should work and quite honestly not even be a hard mechanic as long as you’re watching his cast bar and have a focus taunt macro or something.

Not trying to complain or anything I’m just genuinely baffled by how this mechanic is intended to work smoothly and I’m not the only one as stated by another post on the forums.

Are there any other tanks out there having this issue any feed back would be appreciated especially if its just a matter of skill issue.

For me the taunt swapping mid cast seems to work fine BUT i’ve noticed a different issue with the tank buster. It will randomly apply 2 stacks to someone based on a single cast of Savage Assault. Aka

Casts Savage Assault 1 of 2 on Tank 1
Tank 2 Taunt Swaps
Applies Two Stacks to Tank 1
Casts Savage Assault 2 of 2 on Tank 2
Applies One Stack to Tank 2

And that occurrence of two stacks via one cast seems entirely random and unpredictable. Unless I’m just missing something (which is possible), it’s been bugged for awhile like this with no fix.

The Dungeon Journal’s entry for Savage Assault seems to imply that it only ever should apply one stack per cast, so I would consider seeing 2 stacks in a single cast as the bug. The only change between the entries for normal/Heroic and Mythic is the wound becomes 90% of the unmitigated damage, up from 60%.

Basically, it should work identically to Rygelon’s Corrupting Strikes and associated Corrupted Wound, except Rasha’nan’s DoTs are both combined into the same debuff instead of being two separate debuffs as in Rygelon’s version. Naturally, if the same tank takes a second cast then it will stack, which also happened with Rygelon.