I mean half of that is progress dependent.
For example, early game Brint/Brienne mogs everything.
if you mean the furthest we're at right now (without respect to ultimates) it's probably berserker Atugia. But given she can't be in your party in both slots that's a moot point.
For reference:
- Storm damage so she's the least resisted member of your team
- Boltcloud barrier does cleave adjacent damage (and the 1 extra turn of recharge will nearly never matter given fights don't make it to/past turn 3)
- Berserks if she's hit once which when combined with cornered beast slingshots her to the hardest hitting party member. Allowing her to do Hexblade Cait Shadowstrike or charge weapon buffed Arona's steady strike amounts of damage with her basic attacks (provided both hit)
The only real malus she has is that Stormrage should be adding it's damage on top of a normal attack (like a shock) so she can benefit from weapon buffs and have a better scaling heal. 20-50 hp heal on a (relatively) weak attack that scales terribly and consistently hits less than an at-will attack sucks as much as drain does and is the only real demerit I can give her.