Would love to chat about who's on your Clan Boss team actually, their builds.... and see if we can get a plan to get you into even 3key UNM and 1 key NM.
Arena is mostly just about hitting 1 man teams and such with the loss limits in Gold. Area isn't just the easiest it's even been with those loss limits, people are calling it "comically easy." So that said, it's a great time to medal farm with even a rando collection of things.... and focus exclusively on Clan Boss improvements and getting a great Dragon 20/24 farming team and a team that can beat Doom Tower. :)
If you want to focus on Arena, no worries. But Clan Boss is such a good resource provider for account improvement in the future. :)
Well, for starters, Scyl needs to be off that team ASAP. She's just garbage for CB. The main thing you're missing on your team is Leech. You've already got Deacon at 60, so he'd be a much better fit for your team. Just turn off his A3.
The rest of your team is basically fine, as long as you have Sepulcher Sentinel running 4:3 to put Block Debuffs up in last slot on turn 2. However, doing so means you have no DEF up for the turn 1 attack, which'll hurt. I would probably just drop Ninja, as much as it hurts to suggest. Replace him with Altan, who you also already have at 60. You'll want to set up a rotation such that Altan is last on turn 1, and Sepulcher is last on turn 2.
Here's a good guide for that: https://deadwoodjedi.com/speed-tunes/single-43-block-debuffs/