In Classic, Magic Boost don't affect auto attacks (Unlike Refly, where Magic Attack does affect magic weapon auto attacks)
In Classic, power shards don't affect magic spell damage - they add to your base weapon damage. (In Refly, they boost damage - skills and auto attacks - by 25%)
(Magic spell damage formula is the same for both Classic and Refly - difference is net Magic Boost cap is around 2,900 for early classic, 20,000 for Refly)