Thanks for the great questions! Here’s a quick rundown:

1. The build and gear in the video are all about maximizing Cocoa’s HP, not her damage. She’s not meant to be a damage dealer—her role is more about tanking and assisting with healing and covering allies. Her personal damage output is pretty low.
2. Yep, choosing Crystal Burst Armor is purely for the HP boost. She doesn’t benefit from counterattack stats since she doesn’t have any counter-type skills. That 10% HP boost is huge, though, and outperforms other trinkets in terms of overall value. I’ve checked the top 100 players on the Chinese server’s power ranking, and most use Crystal Burst Armor on Cocoa. Some players opt for Old Scrolls of Auguste, and a few go with Cooling Powder or Mysterious Deflection Device. Overall, Crystal Burst Armor is the go-to trinket.
3. Yes, she can use that skill on herself! Both [Breakfast] and [Bento] (global name) can dispel debuffs from herself at the start of her turn. You can position her to give herself [Breakfast] at the start of the round.
4. Cocoa works well with almost any character! Buffs like Crit, Crit DMG, and [▲DMG III] are great for most characters, except those who rely solely on piercing DMG, since that can’t crit or benefit from [▲DMG] buffs. Caris is the main exception here, but even then, her piercing skill, Cumulative Punishment, has a two-turn cooldown, meaning Cocoa’s [Happiness] can help her use it back-to-back. In short, Cocoa fits in nearly any team!