By the recent interviews Mikael has done recently, he has mentioned that he has been sick a lot on tour due to being in close quarters with so many people, and constantly going into different climates, warm and cold, etc. Maybe that is why things aren't as perfect as you hoped they would be?
Every band suffers this when they tour. Every singer will be in close quarters with other people. You're acting like Opeth is the only band touring the United States to move from a cold state to the beach in a matter of days. All bands do that, and their singers' voices are normally tighter than Mike's voice. Then again, on February 15th Mike said they'd been doing a lot of crack cocaine and heroin. Maybe that has something to do with his cold.