The Oathbow magic item says
When you make a ranged Attack roll with this weapon against your sworn enemy, you have advantage on the roll. In addition, your target gains no benefit from cover, other than total cover, and you suffer no disadvantage due to long range. If the Attack hits, your sworn enemy takes an extra 3d6 piercing damage.
But one of the UA fighter archetypes, Arcane Archer (coming in the Xanatha's Guide next month, but previewed in Unearthed Arcana), has the ability to imbue their arrows with magic and two of them seems like it might conflict with the oathbow's trigger condition.
Piercing Arrow. You use transmutation magic to give your arrow an ethereal quality. When you use this option, you don’t make an attack roll for the attack. Instead, the arrow fires forward in a line that is 1 foot wide and 30 feet long, before disappearing. The arrow passes harmlessly through objects, ignoring cover. Each creature in that line must make a Dexterity saving throw. On a failed save, a target takes damage as if it were hit by the arrow, plus an extra 1d6 piercing damage. On a successful save, a target takes half as much damage.
Seeking Arrow. Using divination magic, you grant your arrow the ability to seek out your target, allowing the arrow to curve and twist its path in search of its prey. When you use this option, you don’t make an attack roll for the attack. Instead, choose one creature you have seen in the past minute. The arrow flies toward that creature, moving around corners if necessary and ignoring three-quarters cover and half cover. If the target is within the weapon’s range and there is a path large enough for the arrow to travel to the target, the target must make a Dexterity saving throw. On a failed save, it takes damage as if it were hit by the arrow, plus an extra 1d6 force damage, and you learn the target’s current location. On a successful save, the target takes half as much damage, and you don’t learn its location.
So how does this work with RAW? I know some situations override things going both ways in favor of exploitation and prevention.
Does the class skill let you bypass the attack roll while getting the oathbow's power buff or do you not get the buff?