I feel the mandatory-card trigger should be a score of 5. If 6 is "average", then if you have determined an entry is below average you'd better be able to come up with two to five words as to WHY it's below average.
Make it even easier -- put checkboxes for common issues like "too salty", "dry", "tough", whatever.
The time issue is a claim without merit. My son is a CBJ and has served at a contest where he judged, was table captain AND had time to generate relevant comment cards when merited. If boxes aren't getting back to the tables in a timely manner, I'd be looking squarely at the reps overseeing the sorting/renumbering of boxes.
Don't practice until you get it right; practice until you can't get it wrong.
Don't overthink or undercook.
180 Brisket -- Sam's Club, Salt Lake City, UT 2014
180 Chicken -- Sam's Club National, Bentonville, AR 2013
Rhythm 'n QUE