Just to throw something else out there - I always found race paces to feel hard during practice. I could never follow programs that recommended workouts based on my race times.
Eventually I stopped worrying about it. The thing is as long as your workouts are getting faster for you, race times will follow.
And yeah that’s a hard workout. 300’s at 800 pace or 600’s at 1500 pace tended to kick my butt. Just make it 200’s and 400’s. If you want to make it harder shorten the rest.