After buying a haircut; game performance is really good. After any dialog the performance is hindered for about a minute, jumping frames, looks unnatural.

Anyone has had the same issue and resolved it?

You're not alone. No solution yet as far as I know.
http://www.gog.com/forum/the_witcher_3_wild_hunt/patch_111_setings_problem

I've noticed that my performance has changed since 1.11. I don't use any mods, nor do I use graphics enhancements - Sweetfx and the likes.

Game sometimes runs smoothly, then micro stutter suddenly introduces it's self. After that it won't go away until maybe I restart the game. Not sure what's going on.

First time I noticed it was when I changed some graphics settings. I believe it was foliage distance and hairworks preset. I'm wondering if something messed up in the configs, so I may try a re-install as my game has been running smoothly before 1.11.

I'm starting to think it's end user issue not the game. I've been testing my CPU's bclk this morning adjusting turbo ratios. Not enough time to confirm it yet though.

CDP RED fixed/improved use of 4 (or more) core CPUs... but in the same time broke 2 core (like mine E8400). Solution is to use additional soft: Fix freezing on dual-core CPUs. It works for me pretty well.