I was testing determination to see the effects for self heals and party heals and got to a conclusion

More determination you have, less heals you get
More determination they have, less heals they get

I did more than 50 heals, increasing determination lowered my health amount

-- My healing stats --


-- Made a self healing test with 10 samples --

With 238 Determination
732 734 733 747 724 753 745 729 729 752
Total Health received: 7378

With 228 Determination
764 726 732 720 724 762 732 741 758 735
Total Health received: 7394


-- Asking a friend to take out 10 determination --

-10 Determination
735 739 754 750 758
Total Health received: 3736

Normal Determination
769 720 740 733 753
Total Health received: 3715

----

Affects the amount of damage dealth by both physical and magic attacks, as well as the amount of HP restored by healing spells