The Eminence in Shadow: Master of Garden World Tree Floor 19

Additional tips and party structure comments below.

Joker:
This boss hits the front most character very hard, so you need a high enough rank tank and a good source of healing. With the team that I used, all of the characters are pretty necessary and hard to switch out with others. John Smith provides bleed immunity as the boss both poisons and bleeds; Claire with her SS+ gear gives extra survivability and basically allows John Smith to live; Gamma and her SS+ gear provides speed and constant healing; Beta and her SS+ gear provides the damage necessary to kill the boss, unless you can remove his damage reduction buff; and Victoria, paired with John Smith, seals the boss and makes him take more damage. This team is taken directly from this video:    • 【カゲマス】次元超越世界樹19階層(ユグドラシル19・恒常キャラのみ)  .

Berserk Wolf:
This boss hits even harder than the previous, and hits the whole party with its jump attack. It is very necessary to have a strong tank, but its even more necessary to have the ability to remove status ailments. The only characters I have that can do this are red support Epsilon with her SS+ gear and blue support Nu, and you have to have mono color parties for those characters to work. As shown in the video, this boss requires more precision than average, so make sure you're watching buffs and timing things correctly. You don't want to use a hidden technique or do a combo for damage when the boss isn't weakened and debuffed. Claire is helpful for the shield she gives to the two Nus since they have low health. If you're having trouble with surviving, try to have your characters at least rank 16. This team is a modified version of what's shown in this video:    • 【カゲマス】次元超越世界樹19階層(ユグドラシル19・恒常キャラのみ)  .

Here are a couple of videos with some different solutions to what I showed:
   • 【カゲマス】次元超越世界樹19階層(ユグドラシル19)  
   • 【カゲマス】自称カゲプロによる解説も要らないユグドラ19層通し【TheEm...  

0:00 - Party details
0:20 - Joker
2:22 - Berserk Wolf