If this turns out to be right, though (and I'm saying it's right until a hard proof) then I will be ready to argue that the rogue is a Tier S

If that turns out to be right, I will probably bump Thief up to S Tier, sure. It still won't compete with Great Weapons for pure DPR, but having two bonus actions is really strong for reasons other then pure DPR.
However, the Rogue base class would still be C Tier. It needs something more. In table top D&D, Rogues get skill expertise and a few other things that Larian have removed, and its left them a little under-powered. I am optimistic that Larian will buff them by full release!
Thanks for the kind words about the writing!