I complete full Tanaan (except throne) every day. I've been doing it for about a year. And there hasn't been such day, when I haven't been asking myself this question - "How would I do this content without flying?". And answer is always the same - I wouldn't. Flaw is always the same - I have to do full daily content. Just because it's mandatory. If I wouldn't do something today - I would fall behind forever, cuz there are no catch up mechanisms, that would allow me to do extra content on some other day, when I would have more free time, like Saturday or Sunday.
And there are many factors, that affect time, needed to complete content + there are factors, that affect accessibility of content. Yeah, when I play Retri Paladin or Blood DK and have overgear - I can just perform chainpull+AOE-fests or even simply kill elite mobs solely. But when I play Mage in quest greens - I have to rely more on quest items, cuz I'm way too weak to kill mobs effectively enough and fat/elite mobs are even deadly for me. Yeah, graveyard - is best friend of classes, like Mage and Priest. Therefore I need to skip mobs to get to quest items faster. Plus competition with other players, that can vary from "dead location" to "completely wiped location".
All this factors cause fluctuations of enjoyment, I get from doing content. Fluctuations from "It's great!" to "I'd better go AFK to wait for things to calm down a little bit". Flying simply gives me some freedom of maneuver. If all mobs are dead within my sight range - I can find mobs to kill within just few seconds. If there are no quest items in sight - same thing. If I neither have some of my CDs, nor cannon balls and there is pack of fat/elite mobs in front of me - I would rather skip it. If my class is still too weak to kill fat mobs (like mobs in Sha'naar) - again, it's better to skip them, cuz high respawn rate is very dangerous - while I try to kill some mobs and spend my CDs on them - others can respawn right behind me. If I still need Fel-Corrupted Appexis Fragments and there is rare mob spawn near me - I should get there within just few seconds, cuz other overgeared players can literally one shot it. If location is completely wiped - I can just fly to another one.
Blizzard need to fix this "instability". My success and enjoyment shouldn't rely on ton of different random factors. If this quest takes 15 minutes to complete - it should require exactly 15 minutes every freakin day. Just one extra player from other faction, who accidentally started doing this quest right at the same time, as me, shouldn't double this time. That's it. Violation of this rule causes burnout, cuz sometimes I'm just too busy or tired to deal with all these extra delays, but the fact, that I HAVE to complete this content RIGHT HERE AND RIGHT NOW make me really angry. And I play game to enjoy it - not to hate it. Delays are deadly for any game. For example Cata failed exactly because players were sitting in 30 minute queues instead of actually playing the game.
P.S. Also I don't even understand, who one can enjoy this grindfest, i.e. killing same constantly respawning mob again, again again. How can one consider it to be immersive? I guess, this idea, that no flying content is "immersive and dangerous" exists only in imagination of some players. Yeah, old no flying content was immersive and dangerous. But no flying - isn't the only factor, that makes content immersive and dangerous. Dangerous and immersive enemies =/= pointless mobs, that are being farmed 24/7 and respawn ever 10 seconds, like they're training dummies.