Each creature you control with power 4 or greater can't be blocked by more than one creature
I am a fan, however, of Devastating Mastery against decks that might have a variety of tricky permanents, but overall I think Azorius needs access to instant speed removal to make a contender and a better choice than Dimir
A spell's mana value is always based on that spell's mana cost, not any additional costs you pay
The devastating auras in this one use the likes of Shardmage's Rescue, Sheltered by Ghosts, and Angelic Destiny defeat any opponents that stumble and don't have the right removal
The first previews we see in the livestream are the rare lands - Bountiful Promenade, Luxury Suite, Morphic Pool, Sea of Clouds, Spire Garden, and Reflecting Pool - all of which you'll be very familiar with if you were a Battlebond fan