within 400y no deer is going to be able to tell whether it was hit by a 308 or a 6.5 creedmoor. they're within 200ftlb of each other between 100-300y, which is SFA when it comes to thin-skinned game like deer.
with less recoil, the 6.5 creed should be easier to become proficient with.
6mms are another option, if even less recoil is preferred. Cabelas had a decent selection of 6mm creed ammo the last time I was there.
if you're comfortable with 308 levels of recoil, take a look at the 6.5 PRC.