I think that the entire 'propose edits' system needs a think. To do a good job of reviewing edits, with 'too minor' in mind, requires a very careful read of the entire post. It's only human nature to see a fix to a conspicuous spello in the title and not see a mistake 'below the fold'. It's even easier to miss other edit-worthy issues.
Once I've gone to all the trouble to vet a spello correction, I find myself torn. It feels petty to click on 'too minor' if, in fact, I've found nothing else to fix. Yet, fixing one spelling error was a silly thing to do in the first place.
In short, reviewing is 10 times harder than making the edits in the first place, so the reviewers are doomed to play catch-up.
In my opinion, the rep threshold for any editing should go (back) up.