Have the same issue. Found a macro after some searching: 
  
/console groundEffectDensity 16 /console groundEffectDist 1 /console horizonfarclip 1305 /console farclip 177 /console characterAmbient 1 /console smallcull 1 /console skycloudlod 1 /console detailDoodadAlpha 1 
  
It reduced the duration of my freezes from 5-15 seconds to 1-3 seconds but it still happens at least once an hour, typically during PvP.