I used to raid pretty hardcore, 4 - 5 times a week in World 100-200 guilds before MoP.
I have to say eventually I burnt out hard. Dragon Soul was the worst, because there were the endless LFR runs with alts etc... I hated the instance when we'd barely started progressing. The mood in the guild was going down, too, some wanted even more in terms of world rank and overall it wasn't fun anymore. I was sort of relieved when we disbanded. It was pretty cut-throat by the end, I didn't like it anymore.
Took a break from WOW after that for SWTOR and eventually came back as a casual. I'd love to raid without pressure, just clearing normal 1 or 2 days a week, but you can barely find that. Back in the day we would clear normalmode on the first day of release, but I can't seem to find that. That's all I'd like, a casual guild that raids 1 or 2 days a week and clears normalmode. Sure, some hardmodes would be great but only what you can work on in 2 days per week without requiring attendance.
I'm fine with signing up in the WOW calendar, but I don't want to have to decline when someone calls me up on a Thursday to go out on Saturday. We didn't raid on Saturday back in the day, but whenever someone would call more or less spontaneously I'd have to decline because of the raiding schedule.
I really like having more flexibility in my life and not having to plan everything around the raiding schedule.
But there don't seem to be any casual guilds with lax attendance requirements that clear normal/start on some heroics without too much pressure. My current guild is very casual and normalmodes are suddenly hard which I find ridiculous. But I don't want a big time commitment, so what can you do...
Gotta say I lost touch with everyone from the pre-raiding days when I was a beginner/casual way back in Burning Crusade. Server transfers would do that to you - when you want to raid harcore, you have to transfer eventually (most likely). We also didn't have much in common anymore. But you do meet new people, make new friends and I'm still playing with a bunch of them who also quit hardcore raiding.
We are all more casual now, doing other stuff like leveling alts or PVP. It's good to be on your own time.