toucanbuzz
No rule is inviolate
If Strahd sticks around, it's supposed to be a cakewalk. These are bane items to him.In my experience, in every incarnation of the module, once the PCs have both the sword and the holy symbol, fighting Strahd is a cakewalk. I would expect the PCs to pretty much ROLF stomp all over Strahd at this point unless he can somehow arrange to steal those particular items.
I prefer to modify my bosses to be like puzzles, with layers to solve and defenses to strip away, rather than just another battle, as a few lucky dice rolls can render what should be an epic finale into a joke. Hence my suggestion that no-way, no-how, would he ever stick around to face anyone with those bane items...unless he's lost all reason and self-control.