Since Erika was recently released, this review should be considered as an early review and things can change in the future for her.
Erika is a Healer who loves to gamble so much, she decided to build her kit around it too - every time she uses any of her skills, she flips a coin and if lady luck favors her, she gives additional effects to Erika's skills. Overall, while RNG-based characters are usually excellent in idle games as you can retry a stage hundreds of times until you win all coin flips, compared to Linzy who actually works like that, Erika is sadly not as good as her kit has several issues.
Erika's strongest skill is her Ultimate - as it gives damage immunity and ATK buff to all allies, and heals them - and the issue is that you will rarely use it on a support character because when you fight under high deficits, you need to kill the enemies as fast as you can. The second issue lies in that she's too focused on being a healer as three of her four skills heal allies. While her Poisonous Potion skill gives her a nice synergy with Jacq as she will debuff the furthest enemy (and decrease their DEF and ATK, which can be good on bosses), it really isn't enough to make her worth using over the other options we have right now - mainly Catherine and Talia. Those two simply give their allies a lot of utility - something that can't be said about Erika. Furthermore, keep in mind that while Erika is all about healing, her Main skill heals only allies close to whoever she targets - so she's better in teams that have a lot of front-line fighters as in most cases the Tank is who will need the healing.
Also, a lot of Erika's utility is locked behind her Artifact - while the base version gives her debuff removal, you need to get her up to L+ to get the upgrade to her Poisonous Potion that allows removes buff from enemies. And honestly, it's not really worth investing into it for PVE.
PVP though is a different beast - there Erika really shines, especially on Defense in the so-called stall teams. Her healing output is so good, she can easily allow your team to survive till the counter hits 0, so whoever attacked you will suffer a defeat.
a lot of healing,
RNG-based kit allows you to repeat a stage till everything goes the way you want,
DEF-shred can be helpful on bosses.
healing output drops when you use a back-line heavy team,
reliance on Artifact upgrades to get more utility,
RNG-based kit - yes, this is both a pro and con as you need to actually get lucky to use Erika in her full form while other characters work out of the box.
Early-game PVE: S
Mid-game PVE: S
Late-game PVE: S