Actually, this is one of the easier opening strategies to disrupt if you handle it correctly. If you look at the flow of playing vs the priestess, you will see that see will be completely reactive for first 4-5 rounds of the game. You will also see that she has two actions per round, and only two, to cast temples and other conjurations. The final point you may notice is that she is not casting creatures at all, so her total action count will remain at 2 for the first part of the game. This where you can gain the tempo edge. Rush her, not with creatures, but with one really annoying ranged or flying creature, and yourself. Stun her as often as you can within those first few rounds, and attack her as much as you can, because then, instead of playing out her temples, she will now be reacting to whatever it is your are doing. And if she is reacting, and not able to continue with her strategy without dying, you are winning. Let's look at actions for a second. The priestess, after four rounds, will have had 8 rounds of actions, assuming she is building, and not with creatures. If you cast a creature during your first turn and then RtB it, you are gaining one action after the first round. Continue that single action advantage for four rounds and now you will have had twelve chances to act to her 8. There should be no reason for her to be casting temples by this point. You want her on the ropes as soon as humanly possible, my good sir, and I can assure you, you will win the game.