I, too, have the jewel of greater awakening. After you get all 12 stones, when you give a subclass to someone, the number of stones you have left just stops decreasing, which is amazing.
Also, about the grinding topic... Well, if you make a balanced team and learn well its strategy, I can assure you, you can complete the main storyline with no grinding that is worth mentioning in a jRPG that is hard, with few exceptions, like
. I'm pretty sure Atlus has made some very good jRPGs in which you need more grinding than that. But then, the grinding in LoT1 is just unbearable. After total 230+ hours of playing that game, I'll give it that.