http://tvtropes.org/pmwiki/pmwiki.php/Main/GameplayAndStorySegregationWhenever possible, it's better to just handwave it rather than forcing a thematic justification.
Besides, this card already have plenty of counters already, removing one of the less used won't hurt the balancing.
SoSa Miracle:
1. SoSa inverts all damage to healing.
2. Miracle heals for (Max HP - current HP - 1)
3. SoSa inverts the healing from Miracle (damage for Max HP - Current HP - 1)
Mechanic is still holds true.
Immortals + SoW:
1. Immortals are "level 2" targetting creatures.
2. Currently Quint and stuff increases creature from "level 1" targetting (not immortals) into "level 2"
3. SoW can only target Level 2 targetting, most of the stuff can only target Level 1 targetting. Shield can affect any level.
Mechanic still holds true.