Spell Power
Description:
Increases critical strike damage bonus by a percentage
Ranks:
Rank 1- Increases critical strike bonus by 25%
Rank 2- Increases critical strike bonus by 50%
Usefulness:

Commentary:
When your spell critically strikes it does 150 percent of its normal damage. With this talent your spell crits will be doing 175% of your normal damage. This can be incredible and it is even more powerful when you combine it with other crit talents like ignite and ice shards or arcane power.

Mind Mastery
Description:
Increases your spell damage by a percentage of your intellect
Ranks:
Rank 1- Spell damage increased by 5% of your intellect
Rank 2- Spell damage increased by 10% of you intellect
Rank 3- Spell damage increased by 15% of your intellect
Rank 4- Spell damage increased by 20% of you intellect
Rank 5- Spell damage increased by 25% of your intellect
Usefulness:

Commentary:
Since deep arcane builds already have a lot of intellect this is a very good boost. This also lets you use gear with more intellect for greater mana efficiency and not take a hit in damage. Anyone who has come this far down the tree needs to take this.

Slow
Description:
Reduces target's movement speed by 50% , increases the time between ranged attacks by 50% and increases casting time by 50%. Lasts 15 seconds. Can only affect one target at a time.
Ranks:
One rank
Usefulness:

Commentary:
After coming all the way down the arcane tree this can be something of a letdown, but it is still a useful spell. It is primarily a PVP spell because it cuts a targets damage output by about half. It can also be an effective escape tool when you need to run and you can't use frost attacks. In PVE it is limited because most raid and instance bosses will be immune to it.

Fire Talents

Improved Fireball
Description:
Decreases the cast time of your fireball
Ranks:
Rank 1- .1 second cast time reduction
Rank 2- .2 second cast time reduction
Rank 3- .3 second cast time reduction
Rank 4- .4 second cast time reduction
Rank 5. .5 second cast time reduction
Usefulness:

Commentary:
Pretty much a requirement for anyone that wants to deal fire damage. It may seem like an insignificant amount, but without it your fireball will take 3.5 seconds to cast. Over the course of a long fight in PVE you will basically get a free fireball every five casts. And in PVP fast casting is a necessity.

Impact
Description:
Gives your spells a chance to stun the target for two seconds.
Ranks:
Rank 1- 2% chance
Rank 2- 4% chance
Rank 3- 6% chance
Rank 4- 8% chance
Rank 5- 10% chance
Usefulness:

Commentary:

This is an incredible PVP talent. A two second stun is incredible, especially when you use it with fire aoe like flamestrike or blast wave and can hit multiple targets. You will not be able to count on it to save you, but it will still help you and your allies.

Ignite
Description:
Your critical strikes with fire spells cause the target to burn for an additional percentage of your spells damage over four seconds.
Ranks:
Rank 1- 8% of your spells damage
Rank 2- 16% of your spells damage
Rank 3- 24% of your spells damage
Rank 4- 32% of your spells damage
Rank 5- 40% of your spells damage
Usefulness:

Commentary:
A requirement of the fire tree. A fire spell will crit for 150% of your normal damage, and if you let this run its course you will have dealt 210% of your spells normal damage. There is the problem that you have to let it damage over time instead of having it hit instantly, and it can be dispelled very easily especially in PVP.

Flame Throwing
Description:
Increases the range of your fire spells.
Ranks:
Rank 1- Range increased by 3 yards
Rank 2- Range increased by 6 yards
Usefulness:

Commentary:
Another semi requirement of the fire tree. Extra distance will help keep you out of range of danger and give you more time to cast in PVP.

Improved Fire Blast
Description:
Reduces the cooldown of your fire blast.
Ranks:
Rank 1- Cool down reduced by .5 seconds
Rank 2- Cool down reduced by 1 second
Rank 3- Cool down reduced by 1.5 seconds
Usefulness:

Commentary:

If you rely on fire for your damage, fireblast will be one of your most powerful weapons. While it is somewhat tricky to use in a raid because of the distance factor, it will be invaluable in small group PVE, solo and PVP.

Incinerate
Description:
Increases the critical strike chance of your fire blast and scorch spells by a percentage.
Ranks:
Rank 1- 2% increased critical strike chance
Rank 2- 4% increased critical strike chance
Usefulness:

Commentary:

Fire blast and scorch are more situational than fireball but this will still help you a lot. You will usually use scorch to make the target vulnerable to fire at the start of a fight, and extra crit will make it more worthwhile. Fireblast by itself is a powerful ability and this makes it better.