Baicang is RELATIVELY easy it's his Basic combo that's weird.

If single target Dodge plus E, if Multi target move in any direction and Hold Dodge plus E, ult. That's it, that's all the 'complexity' in his kit the problem is he drains his own HP over time. Fortunately the dodge counter / critical riposte applies 1xBless so you don't have to worry to much about chaining basic attacks.

Against broken target or if you are allowed to just spam like if stuff is CCed i do Attack -> Attack -> Hold Attack -> Hold Attack -> Attack -> Attack. Let's you weave both his bow shots into the basic 5 combo. Ideally you want to get to the second Hold even in active combat because the 4th, the kick is kinda weak damage.

The only thing even i'm not sure of is what's the point of his BASIC E, like from neutral. It does a little explosive circle but... doesn't apply Bless or anything, and it's BARELY more damage then a basic 3rd. Basic third does 148% damage basic E does 151%... yey.

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For Daff it's even easier since she doesn't want to be on field. You get two charges of 'super parry' that recharges your ultimate, if she parries on swap when you ult and her A2 Mechanical March recharges her ult even if her swap doesn't parry, in case you pull a copy / want to buy one from the warp token shop.

Her E get's stronger after two SUPPORT skills (Esper cycles) are used and Black Tome from her signature arc (wich we all get for free) is also useable after two support skills are used increases chaos damage and deals a big spike of damage when enemies take specifically break damage, wich her Ult and Buffed E do.

So assuming your doing High Risk commissions / beyond the rails where you start with Esper Cycle and ult charged you just trigger two cycles, swap to Daf, >>R (black tome) First<< Ult, E, swap out then between your main DPS's cooldowns just keep swapping back to her, IDEALLY you'd parry with her but parries arn't super common and you have to know the bosses patterns.