QIf I play 2 copies of this spell, does my leader take -2 damage this turn?

AYes, it does.

QDo Strike abilities trigger and resolve before opponents can play cards and abilities with Quick?

AYes. When attacking, all abilities that are triggered must be resolved before non-active players can play cards and abilities with Quick.

QMy leader has at least 11 defense. If my opponent evolves an Azazel after I played this spell this turn, does my leader's defense change to 10?

AYes. Changing defense isn't the same as dealing damage.

QIf I play Jeanne, Despair's Maiden's Fanfare ability after playing this spell this turn, does my leader lose 2 defense?

AYes. Losing defense isn't the same as taking damage.