I like the team Destroyer39 suggested, but I would change the turn order from Aleks and Sinesha. Sinesha does an extra hit when enemies are below 50% of their hp with her A1 (checked after hit no. 1), if a champ like Aleks prepares her attack, she should clean up everything.
That said, the equip of your champs is terrible. It seems, as if you use relentless on everybody, and that set is very good in general. But you miss the stats your champs need. Uugo for example is supposed to put decrease def and block buffs on all enemies. She needs accuracy to do so. 85 acc is way to low, she will fail to land her debuffs. A relentless set let's her cycle through her abilities faster, but just to fail again landing debuffs when the cooldown is over. You don't benefit from the extra turn if your champs can't do what they are supposed to do.
Similar with Aleks. His damage is much to low. You have a chance of 18% to do his much to low damage twice in a row. Aleks without relentless, but 100% crit rate and 200% crit damage would be much more usefull.
The set is great, but if you sacrifice the stats your champs need to complete the set, it's a bad deal.
P.S.
Either way, they should be built with similar builds to Sinesha, though she should still have the best damage gear.
I have to disagree on this one. Gamuran should not have gear like Sinesha (attack and crit), his A3 does neither scale from attack nore can it be a critical hit. Damage is calculated from the hp the enemy corpse had when it was alive only in arena. In boss fights (Ice Golem), the damage from his A3 is taken from his own hp instead.
His A1 and A2 would benefit from attack and crit, but that skills hit like wet noodles anyway, don't waste damage gear on this champ, like I did 🐵. My Gamuran wears a stupid attack% chest. In other words: I tested it, so you don't have to. I'm definetly going to change his gear when I get a nice hp% chest.