There is a scale-up, but it is in oldschool, rpg style - scale-up is bound to the biome you're visiting. That means, you cannot enter a biome without beating the previous biome, first. Or else, mobs will 1-hit tear your **** to pieces.

Just look at "Deathsquitos are impossible" and "How do I get my items back from Plains?" threads to get the full feel of how things are going.