I sorta agree in that each of the biomes could use more places of interest that a player can stumble across when exploring but that could come after fleshing out the main game and then simply bolstering what content is already available.

Rare spawns of larger castles / forts to be found in the world inhabited by fulings or skeletons (which need tougher variants imo) and drauger to be found in plains, mountains and swamps would be a nice addition. Maybe have portals that are either linked to another portal in the world or they are yet unclaimed.

I'd also like to see a lox berserker type of armor.