The problem with assassination rogues is an overly complicated rotation with monitoring various dots and huge button bloat.
We can fix assassination by simply making indiscriminate carnage (a talent that spreads garrotte and rupture to multiple targets when used from stealth) by simply dropping the stealth requirement.
Or
We can alter venomous wound talent (regain 8 Energy each time your Garrote or Rupture deal Bleed damage to a poisoned target) by simply adding crimson tempest.
This would make AoE in mythic more reasonable.
As far as button bloat, remove thistle tea and remove death mark. Give a passive talent like the dream eater dagger in sod that refunds your energy every time to use a finishing move or a talent that reduces the energy required for finishing moves. Something effective and passive.
Kingsbane is fine and Shiv affecting kingsbane is fine and good play
The numbers don’t matter. They can be adjusted to balance so anyone claiming this is overpowered it’s not. This is merely a game play improvement to make the class more enjoyable