You allready got Drexthar, the most important reward from Tag Team before you reach gold and could buy legendary books from the Bazar. Looking at your champion roster, seeing so many top tier champs not leveled up and not ascended, you should concentrate on campaign 12.3 brutal and potion keeps for the next time, not on arena.
That said, you have Cardinal. In a Stonekin set, she is the easiest counter for most speed teams. That doesn't work well in arena defense (attacker may bring a champ with block revive), and as attacker you should not do a line-up where your Cardinal team attacks an enemy with Zavia, Foli or Lydia. But Cardinal in Stoneskin (or, if you don't have that set from the Hydra yet, in immunity with very high hp and def), decrease def champ and two attackers will destroy any speed team the enemy brings. The big advantage of such a team is, that the other 3 teammembers don't have to bother about speed or survivability. They die from the enemies first attack and Cardinal revives them with full turnmeter.
With Arbiter and Deacon you can build a classical speed team. Speed and decrease def allready there, followed by a control champ (for example Giscard, provoke on all enemies) and a nuker (Genbo).