This sounds like an organisational nightmare to be honest. You'd be going through the pile of exams multiple times (at least twice) and what do you do if there are multiple mistakes that are common in a single exam question?
Also: if you're sorting into "mistakes piles" for single exercises, how can you parallelise marking of separate and independent questions?
Also: if you're sorting into "mistakes piles" for single exercises, how can you parallelise marking of separate and independent questions?