Lingering potions of healing/harming have a reduced effect, but this doesn't apply to tipped arrows, which inconsistently use the splash potion damage instead. This could make tipped arrows of healing/harming really overpowered once MC-107856 is fixed.
Expected magic damage:
Arrow of Healing: 2 damage
Arrow of Healing II: 4 damage
Arrow of Harming: 3 damage
Arrow of Harming II: 6 damage
Actual magic damage:
Arrow of Healing: 4 damage
Arrow of Healing II: 8 damage
Arrow of Harming: 6 damage
Arrow of Harming II: 12 damage
So this is blocked by MC-107856?