They are perfect.
They are a pushover once you get the blackmetal shield (or whatever the end game shield was called, it's been a few months), but completely devastating if you encroach on their territory unprepared.

Trolls are no different the first time you venture from the Meadows into the Black Forest. Trolls can 1 shot you if you are not careful.
[Edit]: Nearly every zone has it's own "learning curve" / "increase in difficulty"...
Black Forest: Trolls / hoardes of tree mans
Swamp: Draugr archers and slime (poison damage will kill you)
Plains: Goblins (I forget their official in game names) and Deathsquitos
BONUS STAGE Ocean: Sea Serpent