I agree with you, but monster hunts will be frequent and since Marcin said there will be no presets and we won't have our builds to change quickly, it'll be very boring to take one by one every slot and change it depending on the monster or boss we will face. in the beginning i'm sure it will be interesting and i'll definitely experiment with different skill but since there are 100+ hours i can't imagine doing that all my walkthrough. That's why the balanced or general build as you say it's the best choice imo.
I see now what you mean by presets. It would have been nice to have so you could quickly switch back to your balanced build. Presets in general help players experiment more as well. For example, in "Bravely Default" game, there were no presets, so I was more reluctant to try out a new ability or a new build, as it meant having to change everything from equipment, abilities, jobs etc.
In this case, it's only one set of changes tho, which are the 12 skills. So I am guessing it won't be as huge as a change in Bravely Default. Let's see how it works out.