I am really surprised you had an easier time in the mountains than the swamps, lol

My experience was not dissimilar to yours. I tackled the swamps with fully-upgraded bronze armor, and minor healing mead which I would quaff as a kind of cheap poison resistance - I hadn't discovered poison resistance mead yet!

Definitely died a few times but made it out alive with a decent pile of iron scrap, and exchanged my maxed bronze armor for some level 1 iron.

Went into the mountains biome with my shiny new iron armor and was promptly absolutely murdered by a "You are being hunted..." event. I ended up wasting a TON of frost resistance mead just running around the event area, dying a bunch while I waited for the wolves to disappear. The event lasts for 2 minutes no matter what you do.

The kicker was the mountain was right next to a plains biome, so occasionally deathsquitos would wander over and oneshot me from behind.

What I realized AFTER all of this was that you can place down campfires in the mountains to prevent freezing to death. Would have made my corpse run much easier if I'd thought to bring along some wood and rocks.

I did get my stuff back however and have returned to the swamps for the time being, they practically feel like the meadows compared to the mountains!

I'll return to the mountain when I have maxed out my iron armor...