Proration problem

I have a few questions about this subject.
Is proration shared between pt members?
And one more thing. When i cast magic impact to boss, then I'm waiting finale cast time, If my teammates attack during finale cast time, does my teammates attack count in finale proration?
I know my questions is confusing, but i hope someone can enlighten me. Thank you.

 

Yes, every party member counts. If your party mates spam autos and physical attacks it will boost finale while mid cast.

 

So it did count. Thank you. I guess spamming impact finale won't ruin mages' damage then.

 

If impact hits, it will ruin finale of course. If your party mates spam impact+attack, the impact will boost physical attacks and ruin ur finale(only if impact is the one who only hit and the physical attack missed, anyway you are both screwed)