nothing wrong with adding an isolation exercise at the end, just to pump up the muscle as much as possible. i believe thats why its listed as a high rep set.
doesnt really look too bad. if your goal is bodybuilding, you need to do a variety of exercises. leaving no stone unturned, so to speak. not that you focus on specific weaknesses early on, but making sure everything gets work is a good idea.
it isnt really that much volume, when you look at it. 15-18 total sets. except arm/ ab day, which is around 30, but its 3 muscle groups. im curious how long you have done this or a similar routine, and what results you've seen from it.