When an opponent uses Mystic Reversal on my spell that would be my second card played this turn for Darius, does it still count as my second card played?

Ruling: No, when Mystic Reversal takes control of your spell, it counts as played by your opponent, not you. Cards only count as "played" when they are fully resolved, so the opponent who takes control is the one who "played" it.

Nuances:

• Even though you play the card from hand initially, the opponent gains control and makes new decisions for it
• This means Darius does not get readied or receive +2 from his ability since you did not play a second card