Cleansing fire. Hellfire marker do 1 hit with with 2d6 damage. This means that it hits always and does 2d6 damage but the monster do get their defence?
Yes, you would roll 2D6 damage on each monster and apply their Defense. You always apply an enemy's Defense value unless otherwise stated. For instance, the Judgment "Smite" does D6 damage that ignores the monster's Defense.
Shockwave. Every enemy within 2 space automatically takes 1 hit. What does the automatically mean compare to the above cleansing fire? How much damage does one hit do? If just one damage it wont do much on anything with defence.
Unless otherwise stated, a successful hit by a hero (Sermon, Combat, or Range) does D6 damage with the possibility of some or all of it being blocked by a monster's Defense. In this case you would roll D6 damage individually for each affected enemy and apply their Defense.