Yeah, this game has more than one problem managing "narrative urgency".
Either you are told "YOU ARE GOING TO DIE IN 5 MINUTES" but then you can long-rest an indefinite amount of times (and you need to if you want to experience all the party dynamics), or you are told "YOU ARE GOING TO DIE IN 5 MINUTES" and then you really die because you made the rational call to rush to your salvation only to find an insurmountable fight.
As Tuco said, the fight isn't all that difficult but is just deadly if a player is going to face it as soon as it can (as the in-game lore suggests to do).
First off, nothing in game suggests that you are going to die in 5 minutes. You are reminded multiple times that ceramorphosis duration is about a week. And even Lae'zel tells you that symptoms you might suffer, become more severe the closer you are to your "expiration date", but however many times you rest you are showing none of those. Not to mention multiple times in game you are being told that those tadpoles are diffrent.
Secondly why trusting Lae'zel is a rational thing to do? She is unclear about what the purification might entail, she's alien to Faerun and the way you meet her after Nautoloid crash shows that she would be unable to survive on her own. For me it's clear that she is joining you because she needs you, not other way around. Furthermore, all other companions suggest finding Halsin as a better bet for cure. It takes a big lapse of logic to assume that doing what she wants as soon as possible is the way to go.
As for fight itself, it's not uncommon for cRPGs put fights like that as a barrier. I'd assume that whatever fights wait you on that path later on are even more difficult.
