Yes, it is +104% SS defense. It’s a multiplier that gets applied in this part of the damage formula that has been calculated by players:
In other words, you don’t reduce damage from skills by 104% like it might seem (that would be OP) – instead, the damage you take is reduced by more like 52%.
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You can further reduce the damage if you add in a defense buff too.
With Kadilen and defense buffs mixed in, I’ve gotten enemy snipes to hit for around 300 damage. So with Clarissa you might even be able to reduce it to even less.