I've seen a lot of people saying the geyser isn't spawning and it's making the fight significantly harder having to res after each phase. We found this bug on week one of PTS and submitted a video on how to replicate it but it seems to have made it into live.
Basically just try to either stun the Neirenid at the beginning then burst it down while it's on cooldown, or pay attention and don't kill it while it's stunned. If it dies while stunned, the geyser will not spawn and someone is guaranteed to die.
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