I have a few questions regarding the quest loot, specifically Baal.

I have a sorc that is doing the run and a barb with 840mf and the quest not done.
The sorc downs Baal to 5% and I finish him with the barb, do I get the quest loot if the sorc is in the throne room ?
Should I leave the game with the orginal game creator, or other characters can be in the game/throne room when the barb gets the killing blow ?

Barb not having the quest completed and making the last hit should be all it takes..

as far I know the quest kill is enable / disable by the char who make the game.
Plus, 840 mf seems way too high (diminishing return etc)

I'm interested by the answer

Diminishing returns doesn't mean negative effect. It just means that passed a certain point you get less benefit from having higher MF.
ie 200mf = 10% chance of unique
300mf = 15%
500mf = 16%

Those numbers are made up, but illustrate the fact that more mf = more chance for unique, but not worth it generally since it will affect kill speed.


OP:
The person who creates the game sets up quest/no quest drop.
The person with killing blow will generate MF applied. You could even take it further by having the Barb's Merc to kill the boss to increase mf more.