@Lolikitty
Yeah you did something bad. You assumed he wanted your thoughts on his gear and that he'd take your unwanted advice as gospel. Maybe you were right, but you aren't the raid leader and your mage friend didn't ASK for your advice. You critiqued his gear firstly and then insulted him (mockingly or not, he didn't ask for your opinion remember) and now you're throwing a hissy fit because he basically told you - in a nice way - to shove it ( you want HIM to take advice but when he tells YOU something you sulk..hmmm you might want to think about that too)
If his dps is 'less than stellar' I'm sure he'll lose his raid spot - or perhaps your guild just enjoys his company and doesn't care about his dps? WoW isn't 'all about dps' its about having fun, enjoying people's company AND dps. Relax a little man, have some fun and stop obsessing about what other people are doing, or not doing. You aren't in charge so it's really not your concern.

As for the DISC-overy about the priest (see I can do it too!), I'd keep my mouth shut. He isn't a guild ninja or an account buyer - and you guys get on fine. Let seleeping dogs lie - or in this case, sleeping hunters.