When I delete a post directly from the flag queue, there is no confirmation and the post is immediately deleted. When I delete a post from the question view, I have to confirm the deletion in a dialog.
Deletion is something that can be undone with another click, so I don't really see the need for a confirmation dialog. Moderators delete posts quite often, so saving a click has some value. Allowing to undo an action is a far better solution than a dialog asking for confirmation, there is no reason for a confirmation dialog for actions that are not permanent. Ideally undoing a deletion in a very short timeframe would also avoid create a revision for the deletion/undeletion cycle.
An easy way to prevent erroneous deletion in most cases would to only omit the confirmation dialog for posts that are flagged or that have a negative score. This would prevent misclicks on most valuable posts.