Originally posted by Gisbert:

In Mistlands you no longer have rewards, you just collect and hoard everything. We were facing the Queen and didn't even have 5 cores yet. Then at the end of the biome you unlock stuff you don't need anymore.

Sounds like case of poor RNG or poor exploration efforts. Doing away with the Queen doesn't unlock anything "you don't need anymore" except the Forsaken power. Everything in each existing biome can be found, gathered and farmed before defeating the boss, so your version of the "core mechanics" is pretty colored, to say the least, and doesn't have anything to do with the inconsistent changes implemented in the post-Mistlands patch.