This is a key point; easier to balance different class/builds when their key attributes are defenses. Using this as a starting point, there are 8 different possible triads
Str, Dex, Cha
Str, Dex, Wis
Str, Int, Cha
Str, Int, Wis
Con, Dex, Cha
Con, Dex, Wis
Con, Int, Cha
Con, Int, Wis
Order...