I kind of disagree with that because "just play another combat skill" is not a real solution to me. I'm playing my current skills because I enjoy them or want to level them or want to get gear for them, and don't want to be forced to switch them because they are the "wrong" skill. I'm ok if some things are harder to do, but it shouldn't be impossible.
The spider punt potion for the scorpion dungeons is a great example of allowing players to use any skill combo and still get the knockback, just a bit less conveniently. I kind of want something similar for the ghosts, except not a potion because that's already been done now.
Maybe a solution to the ghosts could be to just have them take a tiny bit more damage than now if they haven't been stunned? I'm ok with them taking longer to die but when playing at level they really can't be killed now without a stun, imo.
I do like the rat trap trick very much and I'm happy to finally have a reason to level gadgeteering but I still think it would be nice if there was something else to allow stun.
Or, I guess, an even simpler solution could be to just have Sir Johnson always assign a different dungeon for the next war cache quest.

I think the main reason this was such a problem for Figger1 is that this one single dungeon was blocking access to all the war caches because the quest kept getting recycled.