GMS Unleashed - bugs and problems

 With 1.5x Buff

Base EXP: 260 EXP
Bonus EXP: 130 EXP
Total: 390 EXP
Multiplier: 390/260 = 1.5x

 With 1.5x and HS

Base EXP: 260 EXP
Bonus EXP: 325 EXP
Total: 585 EXP
Multiplier: 585/260 = 2.25x

So the 1.5x buffs are multiplicative with HS, and I would assume with everything else too.

 With HS and 1.2x Family

Base EXP: 260 EXP
Bonus EXP: 208 EXP
Total: 468 EXP
Multiplier: 468/260 = 1.8x

Family is also multiplicative with HS.

I would pretty much assume at this point that everything is still multiplicative, though we still must test how 2x Events stack (lucky there's an event this weekend), it's just that the bonuses are now on a separate line.

All this does reduce the effectiveness of EXP multipliers at Party Play areas. Oh right, and Items, Link Skills, and Potions that give EXP, since they were already on a separate line and are only calculated off base.