Clearing the first half in 30-45s helps a lot with serpent but you need a very bursty comp to pull it off. I did that one with Diluc/bennet/xq/kaz and kept reseting till i got lucky. Kaz+bennet is particularly good there because
he will always burst pyro and melt the gunners. Then i just try to smack mirror maiden fast as possible. Id say you should try kaz with klee too since he pulls her bombs and boosts her pyro dmg.
Solo hydro Ayato burst does NOT feel reliable for off field freeze against 1-2 enemies but it works against grouped up enemies by venti or kaz. His skill is actually very good for freeze since it applies just enough hydro while having large range so even without strong CC he can freeze 5+ people.
Of course this also depends on teamates and i personally think freeze wise his synergy is ganyu and venti is incredibly busted and trivializes any room with light mobs. Off field cryo you can use Rosaria or Diona, and both enable Ayaka. Anemo wise Sayu is good against small numbers, Kazuha is a significant dps boost, sucrose is copium and jean might be a hindrance. If you're against tough single target (samurai or robot), xinqiu and yelan work with him too.
I dont have all characters but i can tests if you want. I think what most people dont even try ayato freeze is cause they would rather play with Ayaka or ganyu as the field dps instead of him, but he's better for freeze than i thought. I usually start bursting with him, rotate everyone then use his skill and if you kill enemies fast enough his burst will be charged by the time cd is over.
edit: alleged 3.0 banners, this leaker has been trustworthy so far and got a lot stuff right
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Big upsets for my brother who wanted to roll on the weapon banner. I expect the weapons to be tighari's bow + Vortex Vanquish and Amos bow + Koko donut.
btw tighnari's bow is low atk high crit (44%), free 12% elemental dmg and charge attack bonus based on EM, so other than a crit stick it only pops off with tighnari and melt ganyu.