I have a little quibble with this.
While Campaign maps are the best exp/stamina ratio available in game currently (may change with future events), you can't just look at the table for the ratios and base your activity solely on that. Missions in each chapter not only become progressively challenging, but the bosses that randomly pops up corresponds to those missions. The higher level the mission, the higher level the bosses. For example, I farm one map specifically in a chapter, and no matter what happens, the bosses that I encounter are always level capped to that mission (e.g., level 21) This gives several advantages, but mostly in that if you factor in killing the boss in one round, and not expend your "raid energy" beyond that, you could theoretically deal with up to 3 bosses, before having to wait for it to refresh and/or for you to gain your next level.
This may not be important early on, as the levels tend to fly fast, and you have absolutely no time to expend raid energy and/or stamina, but it becomes crucial after a certain point (I think it was around level 12) as you have to be very mindful on what you're planning to do in the game.
Also, there are quests, and players need to be mindful about these as well. Pay attention to exclamation point that may appear indicated a requirement of a quest being fulfilled. Immediately claim your reward, so that any subsequent quest will be active, and you can continue doing whatever it is. For example, if you're increasing affection of a character, the first time you do it after server reset, you fulfill a quest objective. If you keep increasing affection without claiming the reward, you're going to regret it, as the subsequent quest requires the same thing, except three more times.
Stuff like this requires some brain activity, unlike the other offerings from Nutaku.