In highshool I trained as a 400/800 guy (49.9x/1:55) who ran very low mileage, topping out at 45 MPW during cross and around 25-30 mpw during track. We focused a lot of track sessions with short recovery runs and/or strength circuits in between. In college I moved up to 800/1500 training with a lot more mileage my freshman year, running 40-50mpw in the track season, and ran 1:56/4:02. My sophomore year I started doing cross and was doing 50-60mpw in the summer/fall and peaked at 70mpw in cross, then dropped back down to 40-50 during the track season while doing the same track workouts I did the previous year. With all the increase in mileage my performances actually declined, I ran 1:58/4:03. It's also worth noting that times were worse across the board on my team, but I still made the biggest jump in mileage compared to everybody else on my team (even though I was still on the lower end).
Is this a normal timeline of development, and I'm due for much bigger improvement this next season; just an off season; or should I go back to the training style that I was doing in high school?