1. First and most important: Stop making new lvl 50 champs! You will have success nowhere in this game with lvl 50 champs. Bring your actual champs to 60 before you start making new ones. 

2. Jinglehunter (leader, 24% speed aura), Golden Reaper (fastest champ, has to be faster than the fastest enemy to push the turnmeter and speed for the rest of your team), Dhukk (decrease def on all enemies), Zavia.

Use step 1 first, Jinglehunter and Dhukk should be lvl 60 before participating. Zavia is a good nuker, because her A3 has block revive on board.

Turnorder: Golden Reaper (A3), Jingle Hunter (A3), Dhukk (A2), Zavia.

Jinglehunter and Dhukk need 100% c.rate to do their stuff, but they don't need exorbitant crit damage. They are not the damage dealers, they are in the team for decrease def (Dhukk) and reducing the enemies turnmeter (Jinglehunter). You can try gloves with c.rate as main stat on them. Zavia is your damage dealer, she needs 100% c.rate and the best c.damage gear you have. Try to reach 100% c.rate just from substats, so you can use gloves with c.damage as main stat.

I heard Zavia's A3 scales only from ATK, not C.Damage. IDK if this is true, I built mine only with ATK and decent CR and she did well, before she was eventually replaced by a better nuker (Foli and Candy). Never tested her in a classic nuke build.

You are spreading misinformation here. The damage from removed poisons from her A3 is indeed not increased by crit damage (or any other stat, attack does nothing for this as well). But her normal hit damage in this attack is treated as any other damage. It's just a normal hit, and critical damage is calculated as allways. 

And this normal hit damage is still a strong hit: 4.1 x atk with an amazing base attack of 1586.

i'd use the team skadi suggested save that i would substitute gorgorab for jinglehunter. since he boosts your teams turn meters rather than decreasing the opponents, you won't have to worry about it being resisted and his attack buff will make zavia much more effective.

A  Classical  Arena  Speed  team  you  could  make  would  be:

Leader:  Gorgorab 

1st  move:  Golden  Reaper

2nd  move:  Gorgorab 

3rd  move:  Seige  Hulk

4th  move:  Zavia

As  far  as  whether  or  not  the  team  will  be  your  best  set  up,  It  is  to  be  determined.

The  set  up  success  will  depend  greatly  on  how  fast  you  can  get  Golden  Reaper  speed.

Your  Best  Arena  team  would  most  likely have  Rotos  on  it.

The  team  would most  likely be  a  Go  2nd  team.

Leader:  Jareg

1st  move:  Gorgorab 

2nd  move:  Umbral Enchtress

3rd  move:  Rotos

4th  move:  Jareg

You  would need  Jareg  in  a  Shield  gear.

You  would  need  Rotos  in  Resistance gear.

I  don't know  if  you  own  those  gears  or  not.

Indeed I missed Gorgorab, he fits even better than Jinglehunter. Even easier to gear your champs, because Gorgorab, unlike Jinglehunter, doesn't fight with Dhukk and Zavia about the c.rate stuff. Gorgorab needs only speed and some defensive stats, so he can work as reviver if you don't wipe out all enemies in round 1.