Do multiple targets require seperate attack rolls? Or is it one roll against the highest defense?

What power are you using? Or are you talking an attack with ?

If you're talking about making a ranged attack with multiple bolt symbols, it's one attack against all targets. The same goes for Quake and things like that.

This is different than things like Flurry or Duo Attack, which lets you make multiple separate attacks against 1 target each.

Yea sorry it was with three sperate bolts. So you just attack the highest defense. What if each of them have something different on their defense? Like one has super senses one has impervious and the other has prob. Can you use each power for that clix defense?

You are making 1 attack roll and comparing that to each figure's defense individually. You can hit 1 and not the other 2 (or hit 2 and not the third). Prob can be used and the rerolled attack roll is then compared to all 3 defense values.

Super Senses will change a hit to a miss. So that is used before dealing damage.

Once all characters are determined to be hit or missed, you would divide the total amount of damage the attacker does, split that any way you choose among those targets that were hit and then each target may then use their damage reducers, if any.