I resolved the problem. It's 1 of 2 things: I deleted the weapons again and got them again. When I got them I left them in my primary bag. I could now cure the plagued. So, it's one of the two that is the issue.
Originally, I had both weapons in my last bag.
when aphro was trying to do this she deleted both the staff and sword and went and got them again, then she tried it with just staff and then even tried it with staff equiped none of which worked. i think perhaps you just got lucky.
and to HCS about having more than one person on the quest. she was first solo and it didn't work. then tried it with another that was doing the quest too and didn't work then tried replacing and equiping weapons both with that person in the group and without and none of it worked.
I have just tried and it won't cure anymore - I got a new sword as well *sigh*
the sword cull's (kills) the staff cures would need try getting a new staff not sword.