I only said i tested it by spamming it and it didn't bug.
many spells which are casted at same time but are not MUI do not bug.
however there are things which make it non-MUI.
spamming spell is a bad way of testing is spell MUI, but checking code is always the safe method.
i am not saying that every non-MUI spell does not bug so user can see quickly that its non-MUI.
ill tell you why this spell is not MUI.
if we look like this someone uses this spell so trigger is executed and second time someone else casts it trigger is again executed so first trigger reaches its timer limit and it says pick every unit of type... there are 2x of this unit types in map now coz there are 2 casts. i think one cast summons 5 units so if there are 2 casts that means there are now 10 units. His action tells for each of this units cause dummy to cast spell... but wait it should be only 5 units coz this is first cast but his second cast is now executed as well so damage for both spells is done now but second cast is just now to be executed and will deal even more damage.
in fact he will always deal extra damage on spell casts, when casted in less then or equil 1 second right?
so its logical that he will deal this amount of damage
Code:
damage dealt = 100*number of instant casts^2 %
so lets see example you cast it once at a time:
100*1^2 = 100% damage -> good it works well
now cast it 2 times at same time
100*2^2 = 400% damage -> bad two casts deal 400% damage it should be 200%
3 casts at same time
100*3^2 = 900% damage -> bad it should be 300% damage coz 3 casts
i hope you can understand now that its not MUI... and i hope i described it well
try to make it MUI, if you need help and cant find it ask me and ill help you!
~Dark Dragon