I agree that those "surprise! You're dead" phases aren't really great. T5 and T9 has those after 10 minutes of easy stuff.
I can see how T9 must have been for the first groups: Wipe a little bit at phase 1, understand how meteors work and that Ravensbeak is bad. Then you clear that pretty fast, understand the DPS check on golems, organize the group with second meteors, survive mega flare aaand a giant thing kills everyone. Ok, do things again and get pushed to the wall, understanding how Heavesfall works.
Learn Ghosts, understand how to clear Garrote, gets mechanics and clear things. Then Nael starts casting Bahamut's Claw and HOLY MOTHER OF GOD WHAT HAPPENED? After that it's 10 minutes of boring easy stuff until you get to pure chaos that wipe the party in 5 seconds and you have no idea why. You have to record that and watch in slow motion to see what's hitting you, why and in what order. When you finally get it, Divebombs. I love T9, and find the last phase pretty easy, but that's because someone wiped a lot there so I could read a guide and memorize everything. Even then, to find a group that can do everything flawlessly is pretty hard.
I hope Final Coil is different...