GJEH -- As I read your post, you played Valheim after its initial released and progressed through Meadows, Black Forest, and Swamp and, perhaps Mountain and Plains too. The difficulty gap between successive biomes was manageable.

After Mistlands was released, you and your friends find that the transition from the Black Forest to the Swamp is much more difficult than you remember from earlier. As HangarPilot noted, Abominations were added to the Swamp. I don't know whether you had encountered any pre-Mistlands.

I have started over with a new character in a new world several times since Valheim's initial release but not since Mistlands dropped. In my experience, the transition between Black Forest and Swamp can be fairly easy or quite difficult for different playthroughs on different seeds. In some playthroughs, I have encountered no starred Swamp denizens before acquiring enough scrap iron to make suitable weapons and shields. In others, I was greeted upon entering my first patch of Swamp by three starred Draughr. Perhaps you got unlucky with your latest seed.

I don't think you need instruction on how to survive in the Swamp; you already know. I think you have done something that I and a lot of others have not: started a new viking on a new seed after the Mistlands update. Wait and see what players who have done so say about it.