Damage aside, this is an excellent CA for keeping enemies away from the Dragon Mage. After knocking back enemies with Gust of Wind, he can slam a Magic Barrier between himself and them, keeping opponents at a distance while picking them off with damaging spells.
Use this Combat Art to either toss back a group of enemies (if you point somewhere close to your Mage), or to give one enemy a powerful blow (pointing further away from the character), effectively impaling it if aimed well.
The Dragon Mage can impale multiple enemies with a single cast of Gust of Wind by moving closely along the edge of a group immediately after casting. The beam can then impale up to at least six enemies, thus allowing to one-shot small groups. Note that this may be a lag exploit.
When the "Gust of Wind" is focused, 11 projectiles produces instead of 7, and damage to each projectile grown in 2,2 times. It multiplies the base damage, not final, which helps against enemies with high physical armor (large direct damage reduces the armor effectiveness: more armor value enemy has, the greater increase in damage focusing "gust of wind" gives, because increasing base CA damage we reduce a percent of damage that absorbed by opponent's armor).
Great at the end of a combo after one or two combat arts that do heavy damage over time, such as Energy Blaze, Eternal Fire, or a modded Mind Strike. Enemies will be knocked back by the gust, and before they can run back to the Dragon Mage, the damage over time will have depleted their health.
Keep in mind that for some area-of-effect combat arts (Dragon Strike, Destroyers), the gust may actually push the enemies out of harm's way. So it should probably not go in a combo following one of those CA's.
Pros and Cons
100% knockback chance
Can control the angle and radius (wide sweep or focused blast)
If put late in a combo, it might not auto-target the desired enemy (firing in the wrong direction, or at some distant foe rather than a close one).
For one minimal in-game time (1 frame) no more than one hit (flat damage) on the target can cause Damage Over Time\Stun\Knockback, and from this hit a chance to cause these effects is calculated. This means even a million projectiles, simultaneously inflicting damage, have the same chance to cause these effects as one projectile.