I have a question about how dodging works with blast weapons and extra hots from automatic weapons. Let us assume there are multiple creatures within the weapon's blast radius.

All creatures within a blast radius (from, say, a frag grenade get a chance to dodge the blast right?

What about creatures in the blast radius from metal storm rounds (the one I think of as giant buckshot) fired from a heavy bolter? Do creatures get just one Dodge then take the full impact from the rest of the explosions?

For assigning extra hits from automatic fire, do targets being assigned the spillover hits also get a chance to dodge?

Ah the annoying metal storm rounds, source of many conundrums.

We must choose to apply either normal or blast rules for the rounds, the Common Sense Rule demands Metal Storm rounds should be dodged akin to normal ranged attacks. Any you do not dodge then center on the target as blast (2).

Other's hit by the blast may dodge as if a blast weapon. That is, if they aren't too closely packed to prevent each other from getting out of the way.

They are mainly intended for use against hordes, which cannot dodge them anyways.