Mulligan:

Look for Vanndar in opening hand. If you find him, also keep all spells: you want to avoid big minions in your hand until turn 4.
Without Vanndar, you can still stall with removal, or use Faceless Manipulator to copy your opponent's power plays.

Synergies:

Cathedral of Atonement on Undying Disciple is a 5 damage AoE deathrattle.
After your Mi'Da has died, Fragment of Mi'Da is the highest spell in your deck. Primordial Protector draws it and summons a random 6-cost on top!
There are 5 Taunt minions, 3 rushers and 1 Divine Shield minion (Mi'Da) in the deck. Varian will guarantee Mi'Da, if you haven't already drawn it.

Strategy:

Have fun! :)