Good value for a two-mana card depending on the strength of the creatures in your graveyard
Riddleform and Seasoned Hallowblade are solid, and Miscast is essential, but Essence Scatter would probably be better as another bounce spell, Drannith Magistrate might not be necessary (the deck already felt solid against Adventures), and Shell Shield can be a bit clunky and might be better as more copies of Seasoned Hallowblade or Riddleform
So when your summon's time is up and it goes to the graveyard, it's going to trigger Yuna, and she'll pop three or four +1/+1 counters onto another creature, powering it up
The Sideboard Without Soulfire Grand Master but with access to white mana, Valorous Stance gets the nod over Roast as the way to kill big toughness creatures out of Abzan
The other popular gameplay style is Commander, which comprises a 100-card Deck with no repeated cards, and very similar gameplay
You get to look at the top 7 cards of your deck and add any 2 into your hand