Assassinate with Shadow Partner

Why would maxing Boomerang Step make any difference to Assassinate or Shadow Partner?

Bstep also buffs BoT and Shadow Partner with 1.25 bonus.

But I was wrong about this one. The Shadow Partner buff only applies when SP is used with 2nd and 3rd job skills. 1st job and 4th job skills are not affected by the +12.5% damage of Shadow Partner. Double Stab, Disorder, Lucky7, Bstep and Assassinate still have the 50% SP mastery.

Assassinate works like Lan stated, it was mere coincidence that 4*62.5% totals 250%. Just another hypothesis proven wrong!