Its not only 150dmg, and its not the only effect and +the staff original effect that needs to be boosted a bit for the damage as i wrote at the begining the post. Staff effect : 880/1100/1320 to 900/1300/1700 damage , maybe its too much but sure need to be tested as its staff and you get it kinda later on the game while people got atleast a vestment / noms and sometimes idol.
Double stun for staff is too insaine , magmus stun with pk is already great.