I was bored right away, but I did the math and realized that you could get nearly as much QP per apple as you can with 1/2 AP QP dailies, and you get other stuff to boot. My grind was completely calculated.
I couldn't have farmed more if I wanted. From when the sand quest came out until a few hours from the end of the event, whenever I wasn't asleep or not at home I farmed while watching something in the background.
It's good to have at least one or two servants of each class that can hold their own, most of the quests can be beaten just by throwing class advantage at them. And berserkers in particular are good in every quest until camelot or something
Oh, I assumed you were playing JP, whoops
Yeah, she's a limited 4 star only available during the first summer event and its rerun(s?). So you'll have to wait until early August, most likely.
http://fategrandorder.wikia.com/wiki/Kiyohime_(Lancer)
The regular fights aren't a problem but the bosses can be a bit tough. There are no crazy gimmicks like in camelot though, they're mostly just debuff immune and have several HP bars. Probably the biggest handicap is that you're forced to bring Musashi as your support instead of a Merlin or something.