The card Girl Power (B) should give 50% dmg boost and 25% dmg reduction. However, when casting it and another buff on the same unit, e.g. Life Weaving or Unholy Hero, only the buff of the other card actually applies.
Examples:
Girl Power (B) + Life Weaving -> only 50% dmg reduction (expected: 1 - 0.5 * 0.75 = 62.5% reduction, i.e. multiplicative stacking)
Girl Power + Unholy Hero -> only 200% additional dmg (expected: 250% addition dmg, i.e. additive stacking)
Reproducibility:
Tested with Tortugun (R) in forge, where it's bugged everytime. Order of casting of spells doesn't change outcome.
Notes:
Might be a general issue with stacking of buffs. Unity (B) + other dmg reduction buffs also seemed to not stack. Unholy Power + Life Weaving or Unholy Power + Unholy Hero works however.