@Yitra It however depends whether all damaging abilities will have "+/- 25% damage random roll" like Fireball and Magic missiles, thus making difference between low CHA and high CHA up to 50% difference in damage, or if there will be also abilities with reliable damage dependable only on casting stat like Firebolt.
Also devs didn´t state you will always roll better damage, only " you're more likely to roll it", so I wouldn´t count on luck too much - in case of melee fighter I´d rather pick Bear Claws Pendant instead of Rabbit Paw Amulet unless Im tank (although both offer passive bonus as if you had 5 more points in respective stat) - better chance to resist status effects due to save rolls is always valuable and tanking pets sounds nice.
Also concerning the role of luck as DEFENSIVE STAT:
high luck, low resists, medium health
high luck, medium resists, low health
low luck, medium resists, high health
low luck, high resists, medium health
medium luck, medium resists, medium health
medium luck, high resists, low health
medium luck, low resists, high health
--> which of these will offer most "effective healthpoints" ?