Arcane Missiles

Overview

Arcane Missiles is a a channeled Damage over Time spell. It deals arcane damage to a single target with missiles of pure arcane energy.

While you stand and channel, Arcane Missiles launches bolts of arcane energy at your target, dealing the given damage each second. Each second (or "tick") has a chance to crit, dealing 150% damage.
Like all channeled spells, the mana is deducted before channeling starts, so the full cost is paid regardless of how many missiles are actually launched or needed before the spell is interrupted or the target is dead.

Rank	Level	Mana	Duration	Description	Cost
1	8	85	3s channel	Launches missiles for 24 damage/sec.	2
2	16	140	4s channel	Launches missiles for 36 damage/sec.	18
3	24	235	5s channel	Launches missiles for 56 damage/sec.	53
4	32	320	5s channel	Launches missiles for 83 damage/sec.	110
5	40	410	5s channel	Launches missiles for 115 damage/sec.	110
6	48	500	5s channel	Launches missiles for 151 damage/sec.	279
7	56	595	5s channel	Launches missiles for 192 damage/sec.	432

This is the mage's best DPS single-target spell. The long channeling time makes it prone to interruption, especially in PvP, but a full talent upgrade makes it uninterruptable by regular damage, though abilities like [Kick] and shield bash will still stop the casting. When fully upgraded, this is a way to do fast (albiet expensive) damage to something that is trying to kill you with melee weapons.
A helpful talent here is [Arcane Concentration]. A common tactic in groups when so talented is to cast a fast, cheap spell (like [Scorch] or an upgraded [Frostbolt]) until clearcasting is achieved, then cast a free Arcane Missiles.