Field effect damage should definitely require some type of saving throw to either reduce damage or even better, avoid it entirely due to how common it is just like the status effect fields. Barrel explosions should require a saving throw to halve damage too.
It's pretty insane that there's anything that can inflict unavoidable damage with no way to reduce or dodge them at such low levels, which is a big part of the reason why these kinds of mechanics are seen as completely overpowering the source mechanics in importance.
You know, in my original post, I mentioned hoping that modders would remove as much of the Larian cheese as possible if Larian insists on allowing this invasive species to destroy the DnD ecosystem, well, this little mod:
Faerie Fire - No Unavoidable Damage does something small but specific. It removes the guaranteed damage from those surfaces and optionally allows you to roll a Dex saving throw to avoid or take 1D8 fire damage when you start your turn standing on the surface effect. It fixes just this one extremely unfair Larian homebrew, but I hope others will carry on and remove the rest.
Now, I haven't installed any mods yet, so I can't vouch for this one, but no one has reported any bugs so far.
