Cerydra E1 worth it or not ?

Hello everyone I’m actually thinking of getting Cerydra E1, she is E0S1 for the moment, my actual team is Phainon E2S1/Cyrene E2S0/Cerydra E0S1/RMC, her E1 give a big increase for Phainon dmg ? How many % ? Thank you for your help !