Haku's Fan - what to get?

If you mean the 2nd job buff the skill description is wrong, it gives 10%, I tested it. (didn't test if it's a matk or atk based bonus though)

I can't tell for sure whether the 4th job one overwrites it cause the extraction lists them as different effects:
Haku's Blessing (II): Magic Attack: 10% min of Fan Attack Power
Haku's Blessing (IV): Magic Attack: +50%.

The only catch in testing is that when Haku's cast Blessing, it sticks around even if you equip a different weapon. So you have to manually cancel the buff before measuring the range again.

So, should we be scrolling the spare fan with attack scrolls then?