Instead of the never-ending cycle of dumping points into it so you can dump more points into it, how about making the character level determine how many skill slots you get and have your level increase the TP gain as it grows?
Stuffing points into a generally worthless stat that exists to lessen grind by sacrificing future improvement, but encourages more grinding, doesn’t make sense. The higher level you have, the more effort you can put into things, which increases the pace of getting stronger.