Some attacks like chops cause uncanny dodge to trigger on all targets, while spells like arcing spark or jim's magic missile only trigger it on the first target.
Screenshots would have been helpful. I did manage to get Uncanny Dodge trigger on two targets with Jim's Magic Missiles. An Uncanny Dodge card triggers only once per attack card. Maybe your targets were minions with multiple Uncanny Dodges? So when you chop them, the first target evades the attack, then the second target evades too, whereas casting a spell causes the first target to dodge twice*, leaving the other target(s) helpless. *If the first target moves out of reach with the first dodge, the second dodge will trigger for the second target. This is what happened on my screenshot.
Yeah, it must have been 2 uncanny dodges when they both triggered, cause I just can't reproduce it with just one uncanny dodge after quite some attempts. So, nothing to see here folks, carry on.
