Troll Armor is basically your sneaky set, it also comes with no movement speed penalties.
Fully Upgraded it can probably handle the plains if you're a really good player.

Agreed though, this game needs more armors like it for higher tiers.
And it would fit the Viking theme.

Perhaps if they added bears & bear caves to the mountains, and let you craft a more agile bear skin armor.

And to anyone saying "That's just not Valheim." then explain the Troll Armor and high backstab multiplier on dagger.