Question about The Limitless Blue/Bismark Hard Trial

This is my first time doing the trial, so please excuse me noobiness. :)

At the end of the fight, after the last adds were killed and Bismark was about to be reeled in, a person next to me and I were one-shot killed by a bolt of lightning and we both should've had about full hp. There was no indicator on the floor for an attack. I watched MTQCapture's video again for the fight in case I missed something, but she doesn't seem to say anything about it.

Thankfully they managed to finish Bismark without me but how can I avoid dying from this next time? Thank you. :)

When the skies turn purple some water orbs will spawn, do not kill them as they will absorb the hard hitting lightning attack that can 1 shot you if you're not overgeared for the fight.

I'm actually not even 100% sure if there were weather changes in the regular Hard Mode version, my memory is completely filled with the extreme version so someone correct me if I'm wrong.

In Addition the lightning strikes are AoE.

In normal, because of people being synched, the mechanics are a bit more important than in ex (due to being way overgeared). I.e. the bubbles should be only killed on clear and cloudy(? the brownish weather) so they absorb the lightning AoEs.

People tend to ignore that and just destroy all the bubbles all the time, leading to 1-2 deaths in normal (unless it's a tank who gets hit) and, well, nothing really noticeable in ex.

If people killed the water orbs and it's thundering, I'm staying away from other people so that when the lightning does come crashing down, I won't overlap with anybody else. One lightning won't kill anyone so long as the healers are handling things, but two or more people standing close to each other and each person getting hit by lightning causes several instant deaths, as the lightning attacks are AoE, as mentioned above. There is no ground indicator on this attack.