Ok, won't be that hard really. SCV's arn't that much clumbed together + 10 seconds delay how can you NOT seperate them?
If the delay is 10 seconds. Then the 200 damage has merit.
Look at it this way:
Seeker Missile does 100 dmg + area damage. Detonates instantly upon impact.
Widow Mine does 200 dmg + area damage. Detonates after 10 seconds.
Makes sense to me.