Although I don't go out of my way to listen to Disturbed, I have great respect for them. They are selling a lot of records and making a great living from playing music. Bands like this also help to keep metal alive.
Studio work while drunk = not good. On the other hand, I have never done one single session in 10 years without being on the chronic. For me, I become ultra-critical and self-conscious of my work after taking a toke or six. It actually started on the very first record that I produced/engineered. I thought that I was doing a good job, but after I went outside for a toke and came back in the control room everything sounded like horse shit. I'll agree with Andy that it is unprofessional to do in front of your paying clients, unless they're the ones passing it to you. Even then, it's best to turn it down. Skip Saylor used to tell me "Go for a quick walk. You don't want your clients to see you doing that". Another producer that I used to work for told me that he gets loaded on the way to the studio, and that I should do the same. Of course, I didn't listen to either of them. Then again, my main client ended up being the world's most famous rapper - who was on the cover of High Times two years in a row as 'Stoner of the Year'. There are some super-big-timers (like Don Was and Ed Cherney) that light up the moment that they walk into the studio. You can walk into the Record Plant at any given time and know if Ed's working - just by the smell in the air. Many engineers from the L.A. scene (what's left of it) smoke out. Good pot is the cure for boredom.