Another thing about Dummy units that most get wrong - If your Dummy unit doesn't act like a Missile (another obsolete mechanic) then it should be setup as follows: Copy and paste the
Locust -> Set Movement Type = None, Speed Base = 0, Attacks Enabled = None, Model = None, Shadow = None.
That allows it to cast spells "instantly", assuming the spell is setup to be requirement-free.
Also, just to clarify on the trigger:
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Actions
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Set VariableSet TempPoint[0] = (Position of (Triggering unit))
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Special Effect - Create a special effect at TempPoint[0] using AOE.mdx
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Custom script: call RemoveLocation( udg_TempPoint[0] )
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Special Effect - Set Time Scale of (Last created special effect) to 1.65
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Set VariableSet SFX_Destroy_After = 1.40
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Trigger - Run SFX_Destroy_System (ignoring conditions)
The last bit is an example system to handle destroying it, which would either run a Jass function or another trigger that runs some Jass code that detects the (Last created special effect), stores it in a Hashtable along with a Timer, starts the Timer, and Destroys both when the Timer expires.