So your storyboard just defines segues and types, then your view controllers call initWithNib?
That sounds very reasonable. I find IB to be excellent for creating layouts quickly, especially combined with @IBDesignable and @IBInspectable.
My problem with relying on storyboards has been when I need to reuse a layout in a separate workflows. What’s nice about your technique is that it allows separate storyboards but also layout reuse with nibs.