The drop is just fine, but it is somehow has resemblance to how Wheel of Fortune works, ya know, the "2 times per day" thing .. So don't drain your coupons all at once, maybe do it per day for much better chances of getting your desired items ..

Just completed Kushina on my 2nd main account, while my main still needs 31 frags of her for me to upgrade her stars to 4, but i'm not spending on that Great Plates since i'm trying hard to complete my Angel Konan this week, 17 frags to go ..