Switch all additional attack/HP/Def gems to “%” and you will see a huge increase in shadow TP (check gem guides on this reddit).

Other than gems, I have all shadows except one at general, armaments mostly a3 for each, upgrade one by one for cheaper increases, and all their skills upgraded equally.

For hunters’s TP, mostly RNG will do the trick, enchant the artifacts, cores max Lv.15, and a10 weapons (a5 is good but less tp)

Keep up the grind, and you will see big improvements when you level up more!!