I played Kingmaker but I never transformed to an animal so I do not know how they did it.
First of all, each creature has one or several attacks whose damage has nothing to do with the stats.
So the description of an attacks says it causes 2d6 damage, thats it.
I guess the hit chance depends on your stat though.
Druids seem to get more powerful animals over time.
I hope rangers do the same, else their lv3 animal companions will be useless later.

Prof. Dr. Dr. Mad S. Tist

World leading expert of artificial stupidity.
Because there are too many people who work on artificial intelligence already