You obviously don't read very well yourself. Thok will not just become trivial after these changes by any degree. Neither will Seigecrafter or Paragons. If they wanted to honestly make him trivial that would do a flat percentage nerf, and say screw the balancing crap.
Not to mention, even nerfing content to the point that is does become easy for the lower end of progression, there will always be bosses that still require following mechanics to defeat. They don't all just magically turn into stand still and burn fights. At least, not until well after the expansion become irrelevant.