Just use this formula to determine the maximum ST any wizard can use.
https://www.hcobb.com/tft/house_rules.html#Apprentices
That means that a ST 6, DX 9, IQ 17 Molly has only got a total of 18 fatigue of rest per day and with DX 9 less than seven of those points are ever going to do anything.
On the other tentacle, ST 12, DX 12, IQ 8 Merman Don has a total of 36 points of fatigue per day and with DX 12, 26 points will do something useful. That's over three times the amount of effective ST.