The card(normal version) means that for every 100 damage you receive without dying you gain an extra 15% to your overmaxed health when you activate HIVE's ability.
Not that it heals you after receiving 100 damage. It just buffs her ability to overmax health so she gets more when she uses it.
Correct me if I'm wrong. I never used the card since I usually am waiting for my overmaxed health to go away so I can do more damage. More overmaxed health would really cut into your DPS but would make you very tanky.
Just use Explorers, it is the best one.