You all forgetting on one thing! We got few kinds of monsters with different defense, attack, hit rate, evasion, skills, HP etc. So more "critcal mastery" or "deadly mastery" is needed as I told for "another lvl of your toon" to can play normally.
dont mean to flame but do u no how to play ur mage, or at least atempt to play ur mage.
any mage tht can get 30% cast up will b spamming skills non stop, even without there is onli mayb 1 or 2 hits b4 a skill, now iv not got tht high on my mage as i do need to sp farm it and with akan i can, but thts off topic.
there isnt a way of even testing the skills fully b4 buying it lol
also depending on what accs u use tht 1b can go towards some nicer ones, or even getting a crit staff/wand, or as stated b4 crit pots.