Winning isn't the be-all-and-end-all for me, as long as my deck got to do the thing I was hoping it would do.
Scion of the Ur-Dragon offers an easy, repeatable way for you to search out dragons from your deck and put them into your graveyard, which is already a good enough ability on its own for fueling your reanimator cards
If another attack trigger (such as from the mobilize ability) puts creatures onto the battlefield attacking, you can choose to order the triggered abilities so that those creatures enter before Stormbeacon Blade's ability resolves
Getting to do it more is just a bonus if you can play more princesses
This should let Vision do real work in Artifact-focused decks, Voltron lists, and even Control decks that want an evasive threat
If you choose new targets, you must choose the same number of targets