I think the spells are currently very unbalanced, because too many multipliers increase the damage:
Warlock + 50 %, Path of the Mage + 50 %, Evoker + 75 % (25 / 25 / 25), Staff of Souls + 25 %, Ring of Mastery + 25 %, ...
The base damage should be INCREASED and the multipliers should be REDUCED:
Warlock + 25 %, Path of the Mage + 25 %, Evoker + 50 % (15 / 15 / 20), Staff of Souls + 15 %, Ring of Mastery + 15 %, ...
This video (medium map, expert difficulty, dense shards) demonstrates how unbalanced the spells are: https://rapidshare.com/files/2445515040/Spell_Balance.wmv