Today I tried out Crown of the Immaculate EX (Innocence)!
It's labeled extreme, but honestly, tank does not have anything special to do in this fight, you just eat some tankbusters and move the boss around a little bit. It actually feels a little unfair, that DPS and healer have to shoulder so much of the mechanical burden. As far as I am concerned, you can rename it "Tank Swap EX", since there are like 7!! enforced swaps over the course of the fight.
Of course, with that comes a different kind of pressure. With no mechanics and simplified aggro from new tank stance, there is no excuse for low damage from a tank. It's absolutely critical that I do high damage, avoid broken combos, maintain good uptime, and make full use of utility to protect the party from aoe damage (I have to remember to veil and passage on every Light Pillar and Intervention the cotank every time).
The thing that makes this Extreme is the presence of enrage and some of the fastest-paced dodging I have had to do in game, which can get pretty intense at times. Additionally, I have to be alert for players not dropping tethers in the right location and adjust my position not to get hit.
Right now, I am making 2 mistakes mainly.
First, the Winged Reprobation at around 1:56 often hits me as I try to maintain uptime. I just need more practice weaving in and around the aoe's. I actually find most of the latter Winged Reprobations are actually easier for me as a tank.
Second, when the combo of Winged Reprobation + God Ray comes, I must quickly identify if my side is safe and, if needed, not be afraid to cross the arena to the safe side. You can see that there is no safe zone on my side of the arena, and soon the God Ray will expand and hit everything on my side. The safe zone (a narrow pie slice) is on the opposite side, blocked by the boss.
I spent 1 lockout in a practice party, and was able to see up to about the 8th minute of the fight. I'll definitely work hard for a clear!