Lae'Zel - lawful evil
Astarion - chaotic evil
Shadowheart - neutral evil
Wyll - true neutral
Gale - lawful neutral
I agree on the humanoids. All are evidently Evil, from the whole spectrum of the other axis.
The two humans? Both are very "it's ALL about me", nothing Good about them.
Wyll - either, as you say, NN, but I see him as CN.
Gale - LN - hmmm. Maybe? I somehow don't see him as "L anything". Maybe NE but just shy? NN?