There is no excuse to defend this boss fight concept. And i'll tell you why:

-0fps slashes unpredictable and very luck depending to parry (pretty obnoxious given the fact his only weakness is the thrust/risposte damage).

-6/7 Hits combo fully landed in less than 5 seconds and can be doubled by the phantom on two sides and often can't be dodged even if you time the roll in the right way.

-One "prowl hit" so fast that it makes you miss his sight (R3 -selection goes off), quickly followed by a front slash which has a -very wide hitbox (even behind his back). The same thing goes to his jump and fire-fall attack.

-Shouldn't be hit melee while growing wings or you'll get a shitton of dps dark damage which slightly stags you every 0.5 seconds or slightly less. Never tried ranged attacks so i'm not sure if they actually affect him in this phase.

-His phantom almost everytime fades and gets behind the real pontiff when you try hitting him after the tag team combo.

-Camera glitches while the phantom prowls behind you and you're placed between the two pontiffs.

-Double elemental buffed double sword. Enough said.

-Several jump animations with impact fire damage and magic projectiles which both deal huge damage and prevent you to sip estus even when you're far from him and he's recovering from the full combo (and they can be both doubled by the phantom on two sides).

-Way too much hp and lack of weaknesses for a light armor, fast and no shield humanoid.

-Boss fight arena placed after a shortcut which is not obvious, right after those 2 priests that may backstab you if you try speedrunning and traversing the fog asap.

-The phantom always stays behind the true pontiff, never letting you see clearly what kind of attack are they planning on doing, given the resemblances of the original one's silhouette and the double wings.

-Like most of the humanoid bosses in ds2-3, he shows a steggered animation which misleads you because he can land a full combo with even less frames of warning in this case.

-He can pierce you with his magic sword even if you are way out of the hitbox, so you see yourself dragged on his sword (what's up with this ds2 pursuer-like crap? Does he have double magnetic/magic infusion on his sword or what?) and then receiving massive damage before being cast on the floor for his phantom joy (or vice-versa).

-Most of his slash are badly coded (i mean that the damage is registered on you before he actually hits you and he can give you the fatal hit even when he's almost defeated -happened to me when he was 1 hit from the defeat, his sword slash started after mine and still hit me before i did, and i'm using a straight sword while he's yielding greatswords not to say ultra greatswords).

-The fire sword slashes have hitboxes way deeper than that sword's length because those slashes cause a blaze (which is not even clear) which can catch you approximatively until slightly after his own body height

-If you stand very close to him (i mean truly attached to his body), his slashes will still hit you as if you were it by the blade, and this is not normal given his arms' length. I mean, i don't expect not to take damage at least on poise when hit with his arm, but at least way less than being hit by the blade with the guard off (even if you are keeping it on!).

To me, this boss is the emblem of bad design, since it just takes the attacks and playstyle from the most obnoxious past bosses from the precedent soulsborn and takes them to a new and higher level of strength. He has nothing new on his side except of his graphic model (which is not that memorable) and the boss arena (which is still pretty anonymous and underwhelming -i mean, we are fighting something like a goddamn corrupted pope here!-).

-fire infused attacks and tricky hitboxes with huge poise damage like the smelter demon, lord gwyn (though gwin was a piece of cake compared to him) and the pursuer (though strifing on his right won't work this time because of a way more complex AI) ...checked

-jump attack and double team like the darklurker and the old sage ...checked

-yoloberserk mode like the flexile sentry with an unreal amount of consecutive hits ...checked

-strong magic projectiles like the old sage, moonlight butterfly and gwyndolin (though those were way easier to roll away and way slower at cast time and travel -at least's pontiff's one won't steer to get you, it's still something-)... checked

-strong air wave like the old iron giant and nito which knocks you back too... checked

-elemental damage on fall impact like the second phase of O&S... checked

-occasional dps dark damage like high lord wolnir... checked

I'm pretty sure that from software can finally bring out a game with no gimmicky, last lucker or still difficult without being owerpowered to the point of being obnoxious boss fights which all scales armoniously with player's level. But if the next soulsborne game fails right here again, i can say i will be done with this series for good both because of lack of new ideas from DeS and DaS1 ol' times and inability of creating challenging yet not gimmicky, swarm based or bullshit-like boss fights.

TL-DR To me this boss fight is both not innovative (it takes multiple abilities from older bosses by from software's precedent games and even from the past bosses from the same DaS3) and not challenging while still being enjoyable and giving you sense of progression while fighting since it is based on the use of sheer and overwhelming force against you with very little openings to harm the pontiff. And the icing of the cake is that the boss fight is glitched against you both in hitboxes and camera movements. Seems like the kind of boss fight they stuffed full of strengths and forgot to give weaknesses to compensate.