Not talking about going for special achievements or trying to do something the hard way. If you're starting a game and just plan to "win" do you HAVE to grind to get past some of the tough levels?

Well if you change the options in the game to give 300% rewards I do not believe you need to "Grind" really. This was actually a feature they built in to lower that need. You may have to grind ounce or twice before doing something if you build your guys wrong for instance but other than that you should be fine.

Also if you use generic recruits as well their is an option that allows you to give exp to them ALL not just the ones that participate in the battle.