A hard week needs to include something along these lines:
1. 8-10x400 at mile pace or a bit faster. Adjusting the rest anywhere between 60 sec - 3 minutes depending on feel. Ideally, feeling very nauseous at the end of the session. Maybe 6-8 miles total with warm/cool.
2. Some sort of traditional 5k workout, such as 5x1000 or 4x1200 at 3k pace with a 400m jog. I gradually adjust this so that 10 days out from the race, it's 4x1200 at goal pace with a 60 sec jog recovery. Also might tack on a few hard 200's off of very short rest if not feeling exhausted. 8 miles total.
3. 20 minute tempo/cruise intervals/longer tempo. 8 miles total.
4. One, maybe two other easy days of 3 - 4 miles and core work.
In essence, I get way more benefit from running my workouts 'incorrectly'. I improve when I race my workouts. If I get done 4x1200 and feel like I could do one more rep, then I go do another rep and stop when I am totally wiped out. If I don't, my improvement rate is way worse. I avoid injury by backing off the easy mileage instead. I run the 400's until I am dry heaving, or else they don't work that well. Not advice I would give to anyone else, but it is the only way that I ever shave chunks of time.