Siren is the best PvE hero, but not as good in PvP. I’m using her this PvP event, if you’re going to use her, just make sure you have the right healers and shielders. This is my team for this event:
She’s extremely powerful though. Siren’s Song damages all enemies at once and Amplifier buffs the damage massively.
Power Chord also does a lot of damage just to a single enemy. If they’re affected by Siren’s Song, it will automatically recharge. Whenever Siren’s Song expires, Drop It is activated, yet again reducing the cooldown and silences enemies. Over all of that, Amplifier also buffs the damage massively.
Last thing… Astrix is squishy but she’s used in PvE just as much as Siren is :P.