ASW – Alternative hero leveling.

Watch your tongue.
The Blessing Giver provides less benefit, but if that doesn't bother you, then okay.

I wrote everything correctly. What does it give? Less benefit, and so what? Should it be discarded?

It would be useful in defense.
Or somewhere else.

It's not needed anywhere; there are enough perks that reduce spell damage in defense.

Where did you get the information that it doesn't work with zero or negative luck?

It's a well-known bug that the perk only works at 5%, regardless of the presence of luck (except for positive luck).