It looks like, when 2 creatures are 3 squares away diagonally, they are not considered as close enough to be targetted together with Arcing Spark (unless you target another character to make a link). I did not see such problem with Jumpspark
Which sprite is trying to cast the spell? Which pig did you target first? I know that sometimes your targets will be limited because you have to be able to face all the targets at the same time.
I do not pay attention to which sprite casts the spell, I just cannot hit two pigs unless I hit the middle one. As for the need to face all targets, it is not accurate. I could use Arcing Spark, Jumpspark and Gusts Of War on two opposite targets without problems.
In Fanturluche's OP screenshot there is no Sprite that would be unable to face all 4 pigs at the same time so that can't be it.
