My guild only commits 6 hours a week (two days, 3 hours each), we pretty much let people play whatever class they want, we don't force anyone to do the legendary questline, we're mostly friends and family, and we're 2/13 heroic so far with a few more months to get farther in. We went 11/12 H 10m ICC and 6/7 10m H FL, along with picking up at least a few Heroic kills in every tier between ICC and ToT.
It's not about time, it's about attitude.