Per request. Same chart (like Archer) for Sorcery.
http://imgur.com/L4bISyd
Level 55 Sorcery, with Aranzeb's Infusion passive selected, and +5% bonus for all cloth armor.
(1) Look up target MAGIC defense on left. Follow that row to the right columns
(2) Look up column of the skill you want to compare against.
(3) If your magic attack in the box is GREATER than the number shown, Magic Def Penetration is better
(4) If your magic attack in the box is LESS than the number shown. Magic Attack lunagems are better.
Comparison is 10x 30 Magic Penetration lunagems vs. 10x 3 Magic attack lunagems.
http://imgur.com/L4bISyd
Level 55 Sorcery, with Aranzeb's Infusion passive selected, and +5% bonus for all cloth armor.
(1) Look up target MAGIC defense on left. Follow that row to the right columns
(2) Look up column of the skill you want to compare against.
(3) If your magic attack in the box is GREATER than the number shown, Magic Def Penetration is better
(4) If your magic attack in the box is LESS than the number shown. Magic Attack lunagems are better.
Comparison is 10x 30 Magic Penetration lunagems vs. 10x 3 Magic attack lunagems.