Miho is 4 stars fire hero
Skill 1: Fire Hell
The burn is really useful, especially if you pair her with a hero who deal extra damage when the targets are on burn status (such as fire elemental).
Skill 2: Absorb Energy
This regeneration skills is very useful, but the cool down is really long which make this unreliable healing skill.
Trait 1: Grace
Decrease weakening duration by 1 turn. It’s useless because Miho don’t get affected too much from the weakening. Better search for equipment that has a right socket.
Trait 2: Brave (Awaken)
She can tank your party from those one hit KO. Miho is not worth to be used on the PVP if she is not awaken. Miho will only take maximum damage 25% of her HP, if she is awaken the traits will affect entire party, however the effect become 40% Health for other heroes (Miho still has the 25% effect, so don’t need to worry). This will make Miho can tank anything on this game (except multi hitter).
Note: The brave effect still takes effect on your party even if Miho die first.
For equipment, search for Speed, Recover, and Atk power. Why? Read below
Miho doesn’t need critical, because from my observation the regen and burn damage are not affected (CMIIW). Defense and health are not important too, why?
High health won’t important because Miho has low defense and health, so even with boosted health. the damage that the enemy caused still exceed 25% of Miho’s health.
High defense are not important too, because if you really want to make the enemy deal less damage to Miho, then you better to use a real tanker. His strength lies on her brave trait, to recover that damage she gets she need more speed (fasten the cool down and regenerating process). so the conclusion:
 For Round Socket: Ruby (ATK)
 For Triangle Socket:
Emerald (Recover). Yes, it’s not a typo. When it’s useless on (almost) all heroes, it is works good on Miho, because it will increase the regen power, so she can maintain her health above 25%. I was wrong, recover doesn’t affect Miho’s regen so, it’s useless for her.
 For Square Socket: Square socket is super worthless on Miho. Try to avoid this socket.
 For Heart Socket: Ruby (accuracy), to increase her burn chances, or Sapphire (Evasion)
 For Rhombus Socket: Emerald (Speed).
Any damage dealer hero, because they have low defense. If your party consist many tanker heroes, then Miho may not be good on that party.
Fighting against Miho, you need a hero who have multi hit skills (Wukong, Fury, etc). This will pierce through Miho’s brave traits.
Miho is a must for a higher level play. It will prevent all your heroes getting killed by one shot critical hit (such as fire elemental, Tiurel, etc). Only use her if you have awakened her, because Her skills are not that great though.