First and foremost, I assume that you raid and are primarily concerned with raising your group/raid dps. If you are a soloer/duoer, please let us know.
Masters provide both (a) a higher damage range (roughly 14.3% as calculated by Daray in this post:
http://www.eq2flames.com/wizards/119...ard-guide.html), and (b) a lower resistability than do Adept 3s.
Let's assume you are happy with your casting order. If you are looking to increase your zone-wide DPS over the course of a raid, look at a breakdown of your zone-wide DPS from some zones that you frequently raid to understand which spells do how much of your total damage. Note that the relative amount of your total dps that each spell does may change significantly from zone to zone, so it is well worth reviewing a plurality of zone-wide parses. Generally, you will see the largest increase in your zone-wide DPS by mastering the spell that does the largest portion of your total damage (i.e., by adding 14.3% to that number). Likewise, mastering the spell that accounts for the second-largest portion of your total damage should grant you the second-largest increase in your zone-wide DPS, and so on.
I believe that the responses above from other posters are based on the logic described above. One or more have identified Bolt of Ice as being most important to master first, and others have identified Ball of Magma as being most important to master first. Either of these answers can be correct for you, depending on which zone you want to focus your attention on, and your casting order.
I assume that you identified Storming Tempest as being important to master because it is our most DPS-efficient spell. Due to its long recast time and the long period of time over which it does its damage, however, it should not account for a large portion of your zone-wide DPS. While you don't want to use DPS efficiency as the primary determinor for spell mastering priority, there is indirect logic as to why you may still wish to consider it.
As noted above in (b), raising the quality of your spells decreases their resistability. Generally, your casting order at the start of an encounter is determined at least partially based on DPS efficiency. Thus, Storming Tempest is cast very early on. In the early stages of an encounter, however, spell resists are experienced at a higher rate than during later stages of the encounter as the mob(s) may not yet be "fully" debuffed. By improving the quality of those spells that you notice get resisted at the start of encounters, such as Ice Spears, Storming Tempest and Bolt of Ice, you can marginally reduce the chance of spell resists and, thus, increase your zone-wide DPS. AA points spent in corresponding spots in the wizard tree can also help reduce resists.
I hope this helps.
Upgrading to Masters
