I'll even tell you my starter team just because your opinions annoy me so much.
I used UDK, Valerie, Sister and Sorceress. I hadn't yet figured out that defensive toons damage comes from DEF so my UDK did very little damage. I was equipping him with attack stuff. I made sorceress tanky and basically only used her to debuff because she was on the fragile side. Valerie and UDK sheilded and healed. Valerie cleared debuffs and sister did almost all of the damage. With that I could bring down teams of starters and bad UDKs. I didn't start beating decent UDKs before I realized how he needed to be equipped. Valerie was the first rare I skilled.
I tried using warmaiden but decided she was too fragile and would take too much work to make viable. I wanted to beat the enemies in front of me today, not in 2 weeks.
I'm sure your team can beat the teams of other players that have as less experience in the game as you have in lower tier arena. In early arena, account level is taken into the matchmaking. Your opponents don't have a plan how arena works. They are as new in the game as you are. Don't think your victories over them show anything. As Ronda Rousey joined the game recently, I will take her for comparison: a twelve year old schoolgirl may beat up a same aged class mate. That does not help if she would have to fight Ronda Rousey. Neither makes beating up a same aged class mate her a good fighter, nore would the tactics she used in that fight work vs. Ronda. And definetly the 12 year old girl should not try to teach Ronda how to fight.
A well built team of High Khatun, Warmaiden, Starter + free champ nukes your team just away before you can act. UDK could survive, but he has a difficult position 1 vs. 4.
You have no champ in your team that pushes speed. You have no strategy of surviving the first hit of an enemy team, exept of hoping your opponent did not build his champions well and therefore just does not enough damage to kill your champs. UDK protects only vs. single target attacks.
Your debuffer, Sorceress, is a bad champ. Only a (booked) 40% chance to land the debuff, only 3 hits at random. Exchanging her with Warmaiden (campaign farmable rare, drops in campaign stage 9) would immediately upgrade your team. Not because I say so, but because of the objective reason that Warmaiden attacks all enemies and has a (booked) 100% chance to land the decrease def debuff. 100% chance to land the debuff on all enemies vs. 40% chance to land the debuff on 3 random enemies.
That's just one point. As somebody who thinks people should make their own experience, you will learn why your arena team is not good early enough.