We coincidentally just started down this path again after my response on a different project (which at yet doesn't need dynamic data, and we aren't using QML).
So we haven't yet gotten to the original question--sending new data to D3 dynamically--but the basic proof-of-concept embedding of D3.js in a Qt web object (either QWebView or QGraphicsWebView) is very simple: just call XXXWebView::setURL() with the path (either local file or web URL) to your HTML source that uses D3.
The bad news is that dynamically-updating D3 stuff (such as force-directed layouts, but to a lesser extent hover events, etc.) does not seem to perform well in the Qt Webkit view, even on 5.3. The frame rate looks to be several multiples slower than a Webkit browser (this is using the QGraphicsWebView, but I haven't found anything to suspect QWebView would be different).
As for using the WebKit Bridge, we don't know yet. Our use case is simple enough that we could just write new data to a file, and template/rewrite our JS in that event, and reload the HTML from Qt, so that might be an option if your use case is simple or not mission-critical.