I just can't imagine the 'sitting on the bench' aspect of Mythic raiding - I assume guilds have a process of rotating people around to ensure everyone gets a shot.
Because if you are geared enough to be a backup chances are you geared enough to be a starter in one of the many guilds that always seem to need 1-2 people to round out their mythic roster, and with server transfers a relatively cheap and easy thing to do, why wouldn't you go somewhere where you were a part of doing the content rather than being a bystander?
That has to be an immense pain in the ass to manage, keeping those bench folks as active and involved as everyone else.
Being enhancement in a raid with too many melee, I'm pretty much the first melee to get sat every time. As a result, I've been benched to the point that in most weeks I raid maybe 2-4 hours out of our 12 hour week. Sometimes I get more if someone else misses for the night but that's about it. Even farm, I don't usually come in because there's only a couple items that aren't shit for my spec in the instance and other people need loot.
It sucks, straight up. Rotating people around is the last thing you want to do during progression especially. You go through 50-100 attempts and people start getting all those dumb mistakes out of the way, then you introduce someone new to the fight, you get to go through those growing pains all over again and with the way this shit is designed, where 1-2 deaths usually means you're done for that attempt or some mistakes are just a guaranteed wipe almost, just adding one different person just shits on your progress. It's shitty bringing new people to farm for the same reason. No one wants to start wiping again to shit they've beaten and waste time for some people to learn that when there's still more bosses that we need that time to progress on.
I got behind from the very beginning this expac, being the second to last person to get my first legendary in my raid group and the one I got was pretty crappy. Add on being a shitty spec and as always having too many melee and I started sitting early, meaning I get behind on gear, experience, etc. and it's basically just rolled like that through the expac so far (never got a Helya kill, but we only managed to kill it once so not alone there. I still have no Spellblade or Tich kill after 3 kills of them now).
People tell me all the time I should just go find a new guild or something, but I don't want to do that. I love the people in my guild. They're awesome. And it's not our leadership's fault that I got the shaft on legendary luck early (and still continue to get it) or that my spec is fucking garbage. We're a competitive guild and they have to do what they can to make sure we stay that way (also not easy with the retarded amounts of turnover this expac has created). Do I want to be in for stuff more often? Absolutely, but I'm a realist and the reality is I'm just not needed as anything but a backup right now and there's really nothing I can do about it and it's sure as fuck not worth it to drop all the people I've come to enjoy being around just to drop backwards in progression to try and fit myself into a guild that's having such shit roster issues that they'd be desperate enough to take an enh shaman because at that point, they're probably already dead.