The problem is that in Valkyria Chronicles you get a HUGE amount of bonus xp and currency for finishing battles as quickly as possible. Not for killing all enemies or protecting your soldiers, no, for pure speed. Suicide rushes are the best possible tactic. And the rwards you get for that are a game changer. The xp bonus for finishing a mission in record time is twice the base xp, so by rushing you level up three times as fast than if you take it slow.
There are several points about this which make me think that this is bad game design. One is that by making one way to play clearly superior, you give players less options to play their way. The other is that you punish those who persist in trying to play their way. They slowly fall behind in levels until they are way behind the curve and face enemies that are too strong for them. I haven't seen any repeatable fights yet which would allow me to grind xp to catch up if I didn't do well in the earlier battles. Basically you are supposed to save your game before the battle, play it once badly and see the scripted events, then reload and play it better.
I'm all for achievements and badges that encourage you to play well in games. But in a long, linear game if instead of fluff rewards you give out rewards that make you significantly stronger for playing "well", or in a way the devs intended, you get a very perverse effect: You make the game easier for those already playing well, and you make the game harder for those who already have trouble. Shouldn't that be the other way around? Provide more challenge for the stronger players, and boost the weaker ones!