The audits do take a little longer to load. If I remember correctly the bad "suggested edit" audits are generated on the fly by inserting junk phrases into otherwise-good posts, and that requires some CPU time to make it happen (in addition to all the other "audit" bookkeeping the system needs to do).
(Good suggested edit audits are pulled from a list of validated edits, and so are faster.)
As for the suggested edit audits being blatantly obvious, the idea is to catch "robo-reviewers" who are just approving every suggested edit they see (or declining them).
It's specifically designed to catch people who are not looking and just clicking the buttons as fast as they can, so it doesn't really matter how blatantly bad the bad ones are - the people who actually notice that they're terrible edits aren't the target of the audit.
It's a flawed system, but it's (marginally) better than nothing.