1- I honestly don't even have damage meters open anymore. Bosses are dieing at a reasonable pace = I'm happy. You could try working with the other mages who are beating you, for starters, if your low damage is bothering you that much. Normal shit talk between friends/guildmates happens, so far I haven't noticed anything malicious. Yes, I myself am guilty of being harsh sometimes, but I back off poking fun at people if they are getting noticeably upset.
2- There is 180 degrees of difference between having a hardcore mentality to raiding, and getting frustrated to wiping to bosses you've already killed before. I think you are conflating the latter with the former. Sometimes the messing around gets out of hand and the officers/RL has to stop it during attempts if it's interfering with killing the boss. From what I've witnessed, I really think your are reading everything wrong. Nobody is telling people to focus during trash packs / trash bosses. It's always been clamped down on after a wipe to a farm boss or on a boss that is still difficult.
3- No one is pushing to being anything more then casual. Again, I really think YOU are the one reading more into what's happening then what happening. You may be projecting your own insecurities with your #1 reason onto the rest of the team. I haven't heard ANYONE comment about sitting low dps yet this teir. Maybe if we decide as a guild to try a few mythics, but we'll cross that bridge if we come to it.