I'd consider playability first. If it is supposed to work how the DM in the orginal post is depicted to think, then you would need to do every action step by step.
DM: It's the goblins turn. Does anyone want to use an immediate action?
Everyone else: [insert reply]
DM: Goblin attacks the wizard. Does anyone want to use an immediate action?
Everyone else: [insert reply]
DM: The goblin scores a 17 vs. AC. Does anyone want to use an immediate action?
Everyone else: [insert reply]
DM: The goblins rolls 15 points of lightning damage. Does anyone want to use an immediate action?
Everyone else: [insert reply]
Now, that would be certainly possible. I doubt, it's enjoyable.
DM: It's the goblins turn. Does anyone want to use an immediate action?
Everyone else: [insert reply]
DM: Goblin attacks the wizard. Does anyone want to use an immediate action?
Everyone else: [insert reply]
DM: The goblin scores a 17 vs. AC. Does anyone want to use an immediate action?
Everyone else: [insert reply]
DM: The goblins rolls 15 points of lightning damage. Does anyone want to use an immediate action?
Everyone else: [insert reply]
Now, that would be certainly possible. I doubt, it's enjoyable.