Terrible game design persists throughout the third installment of the series.
One of the major design flaws in this game is the necessity to grind at virtually every stage of the game. There are many situations where your party, for whatever reason, is not strong enough to pass a certain portion of the game. You are then forced to use different characters, most of whom are severely underleveled, and grind until they are of comparable level to your main party. If this process still did not work, then you have to repeat the process until you found something that worked.
The entirety of the game can be summarized with this trial-and-error grindfest. Not to mention, in the case you set your skills in a suboptimal way, resetting your skills sets you back 5 levels, which only causes you to grind more.
The "hard" mobs are simply badly designed. The "FOE"s are highly resistant to damage of all sorts, nearly immune to status effects, have infinite uses of skills that hit your entire party (that can be used every round), and have massive HP. There's no sense or strategy to defeating them except to outlevel them.
The designers thought the difficulty would make up for the lack of good game design and this game falls severely short in entertainment value. At times the game feels more like a job than an actual leisure activity.