The idea is to get out of stun faster than Terran can attack if you're under the effect of his slow (+33% attack interval inflicted by Grasping Roots). Weapons with a 2.6 second attack interval will get away in time, however weapons with a 3.0 second interval will not without the use of interval reduction bonuses. Therefore, it is only safe to use Cloudburst Staff while using Surge I or Surge II at this point of progression.
Check if you can idle the dungeon with the Combat Simulator. You can get away from the stun of some creatures in time, so it's hard to use Can I Idle correctly in this case.