[Wotlk] Small Delays.

I have this problem with my gameplay, I get a small delay whenever I cast a spell which is instant when I have good MS.
When I try to cast Vanish or Stealth I get a delay. I've tried to disable addons but it doesn't help! Anyone who knows what the problem might be?
This delay reduces my dps a lot.
I have 50mb download and 2upload internet is not case, and i don't anything in background working except WoW while playing.
My ms is always 50-60 with FPS 60 except in capital city or bg's.
I am using win10 and new WOTLK client.