Absolutely this. The hardest level of personal responsibility I've ever held in this game was defeating Kanrethad (Warlock green fire chain final boss, for those not familiar). Nothing else I've ever done in-game even comes close. If I could hold my entire guild to that level of dedication and performance, I think we'd be 14/14h instead of 2/14h. But that's not who we are as a guild.
I think maybe for just one tier I'd like to full clear on heroic, just so I could have the experience. But I'm also way past my most-hardcore WoW days (in regards to time / emotional investment), so that's unlikely to happen. Oh well.
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"Fault" is not the right word. It's by design, partially, yes. They tune fights so that a certain amount of people clear them. This is much more visible with LFR / Flex where balance adjustments are more frequent and thus noticeable. If in another month or two, not enough guilds have cleared enough of the content (whether normal or heroic), they'll put some nerfs in. Right now they're using the effective nerf of players having time to gear up.