Wrath is simply another word for anger or divine retribution/chastisement. So there would be no evil or good for, rather just it is what it is. Get hit by a lightning bolt, stick your finger in a socket or discharge static electiricty on a doorknob, it's all the same thing, just with different sources. As for paladin immunity, maybe their gods shield them from other's punishment (at a cost), maybe their ability to channel that anger let's them see how to avoid it, similiar to an invoker and his shields. Whatever the reason, I'd say it's fine as is. You know wrath isn't the best way to go if you fight a paladin. You know fire isn't the best way to fight a fire giant either.

"Knowledge speaks, but wisdom listens." - Jimi Hendrix