Before I started studying for OC, I thought the road maps contained all these reactions that we have never seen before, and we would have to memorize them by... "memorizing".
However, after studying for ochem through Chad's videos, I realized I knew more than 90% of the reactions on the roadmap.
If you feel like the roadmap looks like a complete nonsense, I would suggest going back to re-studying Ochem. Also, if you go through the DAT destroyer once, you will be familiar with most of the reactions on the roadmap.
Personally, I don't think it's a overkill at all. It just seems like a table to remind us of all the reactions we have learned.