Like the OP, I experienced a joyful virtually lag free experience for 2 days following U59. However, since the 'fix' the game in now literally unplayable. It takes 10+ minutes to walk across a public zone, such as the Market Place or Eveningstar. This is due to 'constant' freezing and 'elastic banding' back to the previous. On the every rare occasion I can actually zone, I can spend over a minutes swinging at a mob with no hits connecting; and still face the same freezes and elastic banding.
This applies running on both 32 bit and 64 bit client. Running Directx12, so possibly that is an issue?