Commerci sweetwater set

It has been speculated that the drops don't come from the boss, but from some hidden mob down at the bottom of the boat (which we can see because some area-damage skills hit it), which is unkillable by itself but dies after the boss dies. If that is the case, personal drop multipliers won't apply to that mob, since you never hit it. (But a 2x drop event would apply)

So would that mean that classes that do use area-damage skills which hit the hidden mob as part of their bossing routine would get the personal drop multiplier?
That might explain why some players seem to be consistantly luckier with SW drops.