There's two things you need to think about: Damage vs skill damage. Damage is what you do when you do normal attacks, and it is seen in your character stat screen as "Damage: 192-204".

For damage:
1 point of STR = +0.02 damage
1 point of INT = +0.08 damage
1 point of DEX = +0.15 damage

As you can see, DEX adds the most normal damage per 1 attribute point used.

For skill damage:
STR adds more skill damage for bears
DEX adds more skill damage for birds
INT adds more skill damage for mages

But you also have to take into account that skill damage is calculated using a portion of your damage. So bears with high STR can have high skill damage, but bears with STR/DEX can also have high skill damage because DEX increases your damage by a lot, which in turns increases your skill damage.