Siege tanks don't fire missiles, they just instantly do damage. If a unit is killed by the first one to shoot, it happens instantly, so the other tanks don't have a target to shoot. Any instant attack will not overkill.
Not sure you're getting what he's saying. The problem is since the damage is instant the target dies when the first one targets on it thus the rest of them don't get a chance to see it come into range and decide on if they want to fire or not(despite the imperceptible time frame involved, only one thing really happens at a time in a game). What you ideally want is some sort of small artificial delay between the first siege tank picking up a target and firing at it and the damage delt so that the rest of them have a chance to pick up the target and start firing as well. You'll likely want to investigate how to make effects and specifically a persistent one that calls the siege tank's damage to replace the tank's weapon's initial effect.
This is assuming that the visual effects of the siege tank weapon don't heavily rely on the target's presence to show up in the first place, which meh you'll want to look into first.
If a zergling runs by 20 siege tanks, only one shoots. How do I make other units do that too?
Siege tanks don't fire missiles, they just instantly do damage. If a unit is killed by the first one to shoot, it happens instantly, so the other tanks don't have a target to shoot. Any instant attack will not overkill.
How would I make the damage instant and the missle still fire?
@BaridBelMedar: Go
Not sure you're getting what he's saying. The problem is since the damage is instant the target dies when the first one targets on it thus the rest of them don't get a chance to see it come into range and decide on if they want to fire or not(despite the imperceptible time frame involved, only one thing really happens at a time in a game). What you ideally want is some sort of small artificial delay between the first siege tank picking up a target and firing at it and the damage delt so that the rest of them have a chance to pick up the target and start firing as well. You'll likely want to investigate how to make effects and specifically a persistent one that calls the siege tank's damage to replace the tank's weapon's initial effect.
This is assuming that the visual effects of the siege tank weapon don't heavily rely on the target's presence to show up in the first place, which meh you'll want to look into first.