Baldur's Gate : The Sword Coast Chronicles : NWN2 Persistent World

The spell in short is support to give you extra HP and +2 strength with +1 every level and enemy you kill if they failed their save. I killed several gnolls and there was no increase in attributes or HP when they fail their saved.

The increase in HP is temporary HP, which often does not actually visibly show on your character sheet. Typically, though, you should see a temporary hit points buff icon come up.

The increase in Strength does not stack with any other bonuses to Strength. So if you are wearing eg a +2 Str item or buffed with Bull's Strength, there will be no increase.

If you are using the Client Extender, you can run [/effectfade] which should report changes to buff status even from situational and circumstance bonuses, which should aid with validating the effect.