Player one and player two both discard/draw and choose the spells to cast, and player one's spell is cast first, in the same round as player two.
My proposed system:
Player one and player two can both look at their deck and discard/draw as desired, but player one is the only player to cast. The next round, player two will choose what to cast, after player one's actions manifest.
I think this would eliminate much of the disadvantage of going second, and place PvP players on more equal footing. It could also be applied to PvE.