Sorry, I don't buy it.
you are doing 8x400 at 55-58
or 2-3x800 at 2:00
You can run 400 in 50. Never run more than 1.5 miles.
Frankly, if the above is true, your mile time sucks. I was a 4:06 miler. Ran about mid-to-high 51 and 1:53. I could dunk a pass or tip in above the rim if everything was perfect. I could not do your 8x400 workout. I once did 5x400 in 55-57 (with 3 minute rest...or 4 minute. I don't recall). Followed by 12x200 in 28-30. And this was a maximal effort. The type I could only pull off once or twice a year.
I probably could have done a 2x800 in 2:00, but doubtful I could do 3. Maybe with enough rest.
When I was a 4:28 miler (in 11th grade) the best 8x400 I could have pulled off would be at 64 per 400.
You should be bragging about your 400 or 800 speed. Not your mile time.