@Eterlik
I further tested this weapon and its synergies. here is a list.

-Lethargie 100% bonus strike dmg attribut.Only works for the p attack part. Ignores the m attack part.(tested)

-Slithering & Highkick (+200% strike dmg) should be the same as with Lethargie (not tested)

-Running Shot Has no effect on the dmg of the c attacks at all. Guess it simply has no effect on subweapon attacks.(tested)

-Quick cast 50% magic dmg attribute. I think it will not work cause it does not increase the magic attack in the stat screen. but i might be wrong. (**Not Tested** got no wiz3 on 220)

-Crit only works for the p attack part of the attack(tested)

-Swell Left arm p attack and m attack get increased.(tested)

-Swell Right arm as the Power staff is a 2H weapon this buffs gives only 24% evade from attribute. (tested)

-Swell Brain increases Int->magic attack-> increases dmg of the m attack part of the staff. (tested)

-Quicken speeds up the attackspeed (tested)

for further informations see here : https://forum.treeofsavior.com/t/the-truth-about-power-staff/324177