Meteorite is sort of a half-fire storm, hitting ~50% of their creatures until they hit 8 and always the ones you want.
What do you mean by this? Each one only hits three creatures.
If we look only at the middle row and call the slots 1 2 3 4 5 6 7, creatures are played to 4, then 2, then 6, then 3, 5, 1 and 7. Because of this order, the card will hit 1 creature if 1-3 are in play (half-ish), up to 3 creatures (2, 3, 4) if 4 are in play and the same amount with more options if the number is greater. So, ok, my initial proposition was a bit off but basically, it will never kill everything unless they have only 1 creature or have lost them in other ways but will still be a major board wipe at times. Interestingly, your 3rd creature is your safest the majority of the time.