Originally posted by Shillen:

Still seems odd. Every other biome you can level your armor to 4 before going to next biome. Mistlands you can only take it to level 2.

"Before going to next biome" being operative there, currently there is no next biome to go to.
Also no, not really. You need iron to upgrade workbench as necessary to upgrade your troll armour to lvl4.