I've been hunting elk (and stuff) with my .308 Weatherby Vanguard for 7 years now. I think it's plenty. I've put down 4 elk, a mulie and a black bear last year with it, all with either 180gr Barnes XLC, or 180gr Fail Safe.
I've had one elk get away wounded and never recovered - 8 hour track abruptly ended with a vanished blood trail (180gr XLC) - and had one cow that took 4 shots to put down. This one was my fault, first two hits were not well placed, and she had heart. She wouldn't give up, and it's a kill I'm not proud of and learned a lot of lessons on that one.
I had one elk drop, falling towards me and up hill, at about 70 yards with a 180 Fail Safe. DRT. Another I shot at about the same distance running full bore from right to left, she crumpled - double lung.
One thing to bear in mind with this round, of all the game I've taken with it, none of the lethal, put down shots, have been through and through. Short range coupe de grace shots, yes. I have recovered bullets from one elk and my only black bear kills. Both 180s (one XLC, one Fail Safe) expanded nicely and penetrated to the opposite side of the animal. But unlike the rest of the guys at camp shooting 7mm mags, my rounds don't leave exit holes.
I mention this because a lot of hunters seem to think two holes are better than one - and I'm not saying I disagree, only that with the .308 on elk, if pass throughs are important to you, you may want to reconsider.
Tom