No, because it's what actual Medieval priests did as well. Also, priests used to be able to get robbed, then it was changed so they wouldn't get robbed (because they were always getting robbed). I never knew it had been changed back.
So priests should be able to do something to manage the risk; simply reducing the usefulness of the class is not a fix.
I'm sorry. Did a new rule get instituted that as long as something is historically accurate the game must follow it? Read the priest description carefully. Tom spells out they are meant to be a RP class. They are not really designed to be a "useful" class.
Was the change announced though? Priest Couriers are common enough that such a change really should have been announced.
