How Carve a Path works with weapon Winged Blade (Each time you perform an attack, you may change the result of 1 defense die to the die result of your choice)

If I attack three different monsters can I change one die for each of them separately?

I would actually think it's just 1 die total. "Each time" = "once per instance." You're making 1 attack, so you can change the face of 1 die. I'm perfectly OK with the winged blade not synergizing with multi-space attacks- it's already a crazy weapon.

How Carve a Path works with weapon Winged Blade (Each time you perform an attack, you may change the result of 1 defense die to the die result of your choice)

If I attack three different monsters can I change one die for each of them separately?

I would actually think it's just 1 die total. "Each time" = "once per instance." You're making 1 attack, so you can change the face of 1 die. I'm perfectly OK with the winged blade not synergizing with multi-space attacks- it's already a crazy weapon.

That's exactly how I would rule it too. Carve a Path is a single attack affecting multiple monsters, which all roll their own defense pool. The Winged Blade lets you change one defense die amongst all the ones rolled.