How do you people even farm Wyvern 10? I get one shotted at 9 by the wyvern. Is it the gear that sucks for me?
He does his AoE and they all die.
You need to keep 2 debuffs up on him. Right now I use Schuri (He is pretty much the ultimate Wyveren unit, especially if you have the Stars artifact that puts the target up. Even without it he's really good because you can build him for speed and he will push your other units ahead so they can go before Wyveren.) But pretty much Schuri with that Artifact, Kluri (Full kitted out she can keep her def debuff up nearly 100%). And Sez, not only because he does a ton of damage to a fire target, but also his anti-healing debuff counts as one of the two debuffs you need and it has a 100% application rate.
All of your units that do debuffs need 50% effectiveness to make the applications happen consistently. Most of my ring slots are effectiveness for this reason, its a big loss to attack but worth it for Wyv farming (Except Sez, got lucky with his sub stats, he naturally has a lot of effectiveness.) Kluri is also valuable on it not just for her debuff, but also because you can toss that 15% damage transfer artifact on her and it makes surviving the two bolt when you get unlucky A LOT easier. (Its not a problem if it hits your healer or Kluri, but the artifact will make it so even your DPS can survive if they are geared enough. I'm hoping, eventually, to have it so my DPS can survive without--as Kluri with the lance that hastes her when someone else is hit is a lot better IMO, if she's in the back slot and your healer is tanking, it makes her go ridiculously fast combined with her normal haste effects.)
Right now with the above set up, I have a 100% rate on Wyv 9 auto, and about a 70% rate on 10 (Every once in a while, the Wyv will target Schuri right off the bat and because Wyv 10 is still too fast for Schuri to go first, I just need to tank the damage. He can survive thanks to Kluri if he's full life but sometimes and he'll still have some damage left, and that will be a death. I'm hoping I can get his speed up enough soon to make it so I do what I do on Wyv 9, which is have Schuri go first, crit and so the rest of the group will be able to go before Wyv, which makes it a lot easier since the two debuffs get put up and there is no danger of bad targetting.)
But yeah, Schuri is the lynch pin for me. at 180+ Speed and 100% crit he can make most teams work in Wyv 9, especially if you have that Stars artifact. But again, even without it, he makes a lot of compositions possible. If you don't have him, Wanda is also REALLY good since she puts up the target debuff automatically (Build her for a lot of speed so she goes first, she'll toss the target debuff up and you're halfway there getting the Wyv locked down. Along with a very fast Kluri, you should be able to prevent he double attack.)
If its the AE that is getting you, its just a DPS thing. You need to make sure the armor debuff goes up AFTER the shield, since the shield cleanses the debuff. (You really want the debuff up after the shield, since Wyv's turn is slower and you can deal a shit ton of damage with the debuff up). Right now I'm building the Taraner Guard up specifically for this, I might eventually replace Kluri with him, since with double attack and his S1 built up, he'll have a 75% debuff application chance and usually he'll go pretty quick to keep it applied, I think he'll have a higher uptime even than Kluri, and since he's a water DPS, he'll do decent damage.