Since I don't want to sling insults like I accused the original poster of doing, I'll assume as a D2 head coach you just have a lot more support. And I can't speak for other assistants, but we had do the tasks assigned by our head coach. Off the top of my head, here are a few other things: 1) Meeting with athlete's to discuss certain issues, 2) Researching and accumulating recruiting by working through admissions, track results, etc (nights are for phone calls), 3) Planning daily training that might not have been included in that week's microcycle (such as how to manage different groups of hurdlers, sprinters, jumpers men and women when you have 60 of them and no other support staff), 4) documenting yesterday's workout and sending communication to the athletes, 5) research on exercise science to better develop the athletes ie continuing education, 6) travel planning, expense reports, etc. 7) handling recruiting trips, 8) uniform management for 100+ kids, 9) home meet planning, 10) working with the strength and conditioning coach 11) meet with other people in the department for various reasons 12) big projects such as building a new facility, relocating within a facility, etc. 13) building a schedule for the next season, not easy in certain parts of the country where there are few meets and the D1 schools don't want you there, 14) entering kids into the meet which can be tedious when trying to get kids into the right heat, 15) googling stupid crap that your asinine head coach can't manage to google for themselves, 16) coming up with a strategy for conference championships - such as what events to enter kids, how to attack a certain event that might be easy to score points, relay strategies [how many people spend at least 5-10 hours a week on their fantasy football championship], 17) injury management, 18) working with sports information and luckily I did end up doing much of this one, but I know it is a big responsibility for many D3 programs... 19) fundraising.
In my stints of coaching, I always took sprint programs within the first year from 0-1 All Americans to 5-10 All Americans and 20-50 conference points to 200+ conference points. Again, in any job I usually have a list of things I need to accomplish to make my team or company better. On top of that I would leave the Monday morning staff meetings with a list of 10-15 things I was supposed to get done that week assigned by my head coach (and yes I was required to be in the office/facility from 10am-4pm every weekday). I agree that I would have structured things very differently than my 3 head coaches. But in the end, whether you own your own business, coach a team or have a corporate job, there is usually a lot of important duties you need to do to be successful that requires 30+ hours of office work. Just my opinion. We don't need to agree, but I think a lot of other full-time assistant coaches would find my story relatable.