If it's low rep and you're using it specifically as a main movement for deadlift as part of a powerlifting program, then use your competition grip, whether that's mixed, hook, etc. Note that if you mixed grip, one way will feel more natural than the other...this is because no one's shoulders are built perfectly evenly and one most likely will be slightly more internally rotated than the other, so that's fine, use whichever way is natural.
If it's high rep or not part of a powerlifting program, use straps. No reason to hold back your posterior chain because of grip issues.