I’m sort of assuming Blizzard hotfixed Sunder Charms by reverting them to a prior version of themselves, in order to fix the Find Item guaranteed drop bug that’s been going since Ladder started.
In the process, it seems like it reverted the Charms to a version where Traps/Pets working with the Immunity break don’t work.
I can see the mobs no longer being Lightning Immune on my Trapsin, but they’re taking 0 damage from the Traps.