I know Mythic is harder than Heroic which is harder than normal. LFR is the easiest. But in terms of difficulty to the groups, I can say I had an easier time clearing Heroic than LFR. I was part of a LFR today. Several people said it was their first time. I took the time to explain the fight. Still, on the first try withing a minute we lost about 8 people. I was getting frustrated so I explained again, it was better second try, even better 3rd try, but I didn’t have the patience to stick around for 10 stacks of determination so I left. Again, prior to Nzoth, I always thought determination only went up to 5 stacks, because I have never seen 10 stacks in my entire LFR xp. So that should tell you something. Your experience maybe different, but this has been my xp.