Biggest problem with LFR N’zoth, imo, is that it punishes the group when individuals fail mechanics.
Obviously in Normal and up that works, but in LFR it just causes problems.
The 10 stacks of determination don’t make people use the extra action button.
They don’t make people go in the portal.
They don’t focus down a player who gets MC’d.
They don’t make people stand in range of tentacles.
LFR can’t reliably do that many mechanics, anyone remember Nazgrim LFR pre-nerf?