Like you I was more of a 4/8 in high school and did extremely low mileage in high school. 10-15 mpw with a lot of races and tempo runs and fartlek. I wasn't as fast as your high school times but I'll write about my college training and progression to counteract the high mileage 800 bandwagon.
Year 1: Did XC for the first time instead of playing high football and basketball. Ran indoor and outdoor track. For indoor and outdoor I trained with the distance team. For the indoor season my 800 was 3 secs off my high school PR even though I had run a ton of XC miles and trained for track instead of basketball. I thought I would be crushing my high school times because now I was doing 16 mile runs and running 3x4 times more miles! For outdoors my 1500/mile time improved by over 5 seconds but saw no improvement in the 800. I ran the 800 at conference with mono and equaled my high school PR.
Year 2: Did XC for second time ever and improved by nearly a minute in a half. 26:18 8K. However I trained indoor and outdoor as a 600/800/1600 relay runner with the sprint team. Indoors saw a slight improvement from the prior season but nothing notable. For outdoors I dropped 3 seconds off of HS PR in the 800 and 2 secs for 400 relay split.
Year 3. Did XC for third year but missed two weeks due to illness so no improvement. Trained again as a a 600/800/1600 relay runner with sprint team for indoor/outdoor. Indoor saw slight improvement from prior season but nothing to be excited about. Outdoor dropped 5 seconds from HS PR and nearly 2 seconds from college best. 400 relay split dropped by .5 seconds.
Year 4: Studied abroad and worked out about 3 times a week via email from track coach. Took about three weeks off traveling from mid Dec to Jan. Trained with sprint team again. Set indoor PRs in 600/800. Improved outdoor 800 PR by half a second despite missing 1.5 weeks of training with a strained hamstring. 400 split remained about the same as previous year.
Our college team def undertrained early and could peak at the right time. In the beginning of the season our times would be dogsh*t slow compared to our competition but our coach would tell us to wait a few months and then compare. Sure enough we improved steadily while many other schools struggled to stay healthy and hold form. The caveat is the 6/8 guys did hardly any aerobic work and I feel like I would have benefited like Quamel Prince from doing more easy miles and a tempo run.
Looking back at my training, I didn't gain much from running XC. Indoor season was spent gaining back lost speed during XC. Training freshman year with a distance focus improved my 1500/1600 but the 800 hadn't shown much during outdoor. My freshman 400 speed was pretty poor considering how aerobically fit I was compared to HS. When I trained years 2-4 more like a sprinter the 6/8 times steadily improved. Senior track season was the best despite not running XC, taking nearly a month off in the winter, suffering a hamstring injury while trying to finish a senior thesis/graduate, and find a job the last few months of school. Not all mid distance runners have to train like Lord Coe .
http://citiusmag.com/quamel-prince-underdog-story/