Polarizing Strikes

Pandora will fire a line stack AoE on her left and right sides up to four times, which is meant to be stacked by four players each.

By far the easiest mechanic in this phase, this mechanic is essentially a heal check that becomes dangerous if the party does not mitigate these attacks.

Polarizing Strikes

Pandora will fire a light AoE on her left side and a dark AoE on her right side. The person in front will be inflicted with a resistance down of the element they're soaking, forcing them to switch sides in order to avoid taking a fatal hit that they have a resistance down on. The lineup order is Tanks, Melee, Ranged and Healers, with light party 1 on the left side and light party 2 on the right side while facing the boss.

Lineup behind the boss where the flank/rear of the hitbox meets. Make absolutely sure to check where the boss is facing! Do not assume true north here, because there is no guarantee here that the boss is pointed at north. Make sure that the tanks are inside the hitbox of Pandora, everyone else should be outside behind the tank. Pandora targets one random player on each side, so you do not have to worry about proximity.
Pandora fires off her line AoEs, inflicting a resistance down on the tanks at front. Immediately get out of the line AoE as it will explode soon, inflicting a damage down and possible a death if you stay in it. For reference, you can assume the snapshot has already occurred every time the castbar disappears.
The line AoEs explodes with a "shing shing shing" sound effect. This is your cue to run back into the line, because the snapshot has already occurred for the line AoE.
The tanks have a resistance down, so they cannot take another hit of the same element. Have each tank switch to the other party in the lineup. For the 2nd hit, have D1 and D2 stand in front to soak the resistance down. This process will be repeated until Pandora has attacked four times.
Repeat again, but this time with D3 and D4 in front. D1 and D2 should switch to the other party.
Most guides or reference will tell you to have healers be in the front for the final hit, but in reality, it does not matter who is in the front at this point. All it does is inflict a player with both a Light and Dark resistance down if a non-healer is at the front, which will expire anyway as this mechanic is resolved once the fourth Polarizing Paths has been soaked. There is nothing stopping you as a healer to go the front anyway though, but keep in mind that its extra movement if you choose to do so.