i agree with the majority of people here. I've seen Mastodon 5 times. I absolutely love them as a band... but 3 out of the 5 times, they sounded like shit live.. and it was because of brent. one of these times was before his head trauma. There's really no excuse to make for him... head trauma or not.. the guy openly admits to doing drugs and drinking in excess on a regular basis. it has a huge detrimental effect on his stage performance.
It's true, he is the primary song writer.. and writes some amazing and brilliant music... but his wreckless lifestyle and asshole attitude are the downfall of the band's live shows. It's bound to come to a head sometime, unfortunately. he just needs to get it together.