Oath of Enmity explicitly states that if an effect makes you reroll and you rolled twice because of of the Oath, you reroll both dice.
Oath of EnmityDDI
If an effect lets you reroll an attack roll and you rolled twice because of this power, you reroll both dice.
That's the case of Elven Accuracy.
With an instant of focus, you take careful aim at your foe and strike with the legendary accuracy of the elves.
Free Action - Personal
Trigger: You make an attack roll and dislike the result.
Effect: Reroll the attack roll. Use the second roll, even if it’s lower.
Now, Wild Elf Luck allows to add a +1d4 to the reroll when you use Elven Accuracy.
Wild Elf LuckDDI
Benefit: When you use your elven accuracy power, you gain a +1d4 bonus to the reroll.
Special: You cannot select this feat if you have the Wood Elf Agility feat.
I see at least 4 ways of interpreting it.
- You roll 1d4 and add the result to one d20 roll only
- You roll 1d4 and add the result to both your d20 rolls
x=d4, max(d20+x, d20+x)
- You roll 1d4 and add the result to the best of your d20 rolls
- You roll 1d4 and add the result to the first d20 roll, then roll another 1d4 and add the result to the second d20 roll
Option #2 and option #3 seem equivalent, but I'll opt for #3 because Oath of Enmity transforms the "reroll" into the best of two d20 rolls (
max(d20, d20)), then Wild Elf Luck kicks in by adding 1d4 to the reroll result (
So, answering to your question, Wild Elf Luck behaves as applying to both rolls, even if it applies to the best of the two.
Difference between #2 and #3 could become important under other circumstances.