I'm sorry to be the one to say it but that whole performance was incredibly sloppy. I usually expect much better from Opeth, though I guess I can let this one go since they have not had as much practice playing this song live. Even Mike's vocals were terribly off-key. The harmonized part at the end was really bad too, one of them was very noticeably flat through the whole thing.
I just hope they brush this up quite a bit by the time I see them in concert. It would be very awkward if I was in the audience singing the right notes while they sang the wrong ones on stage.