The idea is to get out of stun faster than Terran can attack if you're under his slow.
2.6s weapons will get away in time, 3.0s will not.
Therefore, Cloudburst Staff is impossible to use at least 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.