Based on articles I've read, you'll need to power up a shadow ball gengar with Def15&Sta15 to level 32 to survive taking 3 confusions in order to get the shadow ball off. The difference between getting off the shadow ball is between being good and terrible.
Based on attack break points you'd need to power up #1 to lev 33.5 and #3 to Lv 31.5 to get another fast point. But you'll get many more shadow claws in compared to hexes.