You shouldn't bother using AMR unless you're going against Bosses (those giant things in 1-4, 2-4, 3-5...). Anything else is just a waste. You should swap her with an LMG/SR/AR which are better choices for infantry units.
As for my take on the game, it was more or less a good game. A bit of grindy, yes but that's already expected. My only two problems are: the game loads too slowly and the battles are resource hungry. Each click of any button takes 3~5 seconds to load, sometimes longer. Although this might be because my laptop or connection being just slow.
In any case, I love the girls and their character designs. I specially love So Shiguchi. She's already a hottie with her short hair. Wait 'til it's longer and you have a goddess.