Mastery of the Arcane is only half effective. 15 % instead of 30 %.
Mastery of the Arcane 0:
Buffing yellow d/q as cleric 50 buff yields to +78 d/q
Mastery of the Arcane 9:
Buffing yellow d/q as cleric 50 buff yields to +90 d/q
So its 1.15 the value and hence 15 % buff bonus.
It says 30 % bonus in the discribtion,
Mastery of the Arcane 0:
Buffing yellow d/q as cleric 50 buff yields to +78 d/q
Mastery of the Arcane 9:
Buffing yellow d/q as cleric 50 buff yields to +90 d/q
So its 1.15 the value and hence 15 % buff bonus.
It says 30 % bonus in the discribtion,