Your rant sounds very much like me at the end of my last raiding bout on a previous MMO. And yes, it is hard to say no when you know that people feel you are pivotal to the raid's success. But if you continue to do so, it's a sure path to burn out. A hard burn out. And that's so not where you want to be before a brand new flashy xpac hits.

It's not fair to you or your raiding group to carry this much weight on your shoulders. As Redbeard pointed out... if you burn out, nobody gets to play wif ya. Set your boundaries and stick to them. Screw the dissapointment. Do not let something that is supposed to be a joy, be a burden.
My recent post Do Not Want