The Player's Handbook states that when cast as a 3rd level or higher spell, Blindness/Deafness can target additional targets equal to the difference between the spell slot the spell is cast at and its base spell slot level of 2.
My question is, would it be legal to cast Blindness/Deafness as a 3rd level spell, but instead of having either effect (blindness OR deafness) target two creatures, have it target one creature with both effects (blindness AND deafness.)
I'm having a hard time deciding whether this would provide an overpowered effect, as it increases the amount of disabilities one creature will suffer from, but lessens the number of creatures affected by the spell.
Perhaps it could be legal provided the targeted creature gets to make a separate CON save against each effect?