So the reason you can't avoid his stormbolt is because its a dummy? 0_0 I didn't know.
Well, "technically" you "can" imitate the behaviour of the default Storm Bolt (blink to evade it) but it requires more advance triggering and could lose precision of the spell.
Therefore, a simple coding does the job perfectly.
But if you still want to do it, first you need to register every single ability that has this mechanics (possible to avoid via blinking).
Next, if the target blinks away
after the projectile has been created, directly change the flight path of the projectile to the
initial location of the target
Upon arriving the location, kill the projectile.
You don't even need "timing" in Warcraft III to evade the projectile.
The condition is simple: Blink when the caster spawns the projectile
at any time before you were hit by the projectile
Even if the caster is 10,000 range away from the target, and right after caster spawns the projectile, you can immediately blink to anywhere you want (you can even blink to the same place) without getting hit.
This mechanic is from default Warcraft III engine.