I agree with this. It's a bit like the first 2 pancakes, you have to go back over the first half a dozen once you're in the zone.
I used to grade hard copies a lot, after I graded I'd put them in order from best to worst (numerical grades) and then do quick comparisons between an assignment and its neighbours in the pile. It's an easy way to "quality control".
As for the comments, that's a self-discipline issue. If you're giving, say, 4 positives and 4 negatives per assignment and have standard ways of phrasing, it shouldn't deteriorate.