exept T5 is not hard, but ask to know perfectly all the pattern of the boss like... well all the fight of the game. no difficulty there outside have 7 other people that know the fight like you.
DF is not something you must use for training, i found it soo much stupid... how can you train efficiently with different people all the time... how can you become better if each time you have a new group? this fight ask your group to dance together... one person that mess up and it's over... you can't expect to have a whole group in DF that know all this freaking pattern that make this game boring as hell!

because that the real trouble of FF14, the fight mechanic are soo dumb... why make us do dance instead to fight monster? when you know the pattern perfectly you can simply put your brain on the table and do it in auto-pilot... not because you are over-equiped, but because if you follow the pattern the fight it's beaten everytime!

anyway, why T5 is still a trouble? because it was artificially make in a way to be harder, the dive, twister are a perfect example of it. ohh and a lot of people that pass T6 find it way easier than T5 then stop to come say, you will not pass T6 because you can gather 7 other people knowing a dance.

we have get that the raid guild around want instant gratification win with no real difficulty outside dance together... not need to be hard with other person pointing a flaws of the game.