I had success beating this team in arena with s.naruto,k.gaara,GNW kankuro and fm. But I like to use my Hidan :P (post 1 ,1st team https://forum-narutoen.oasgames.com/page/show-post-24256-1.html )

Here's a team anyone with 400 scrolls can field that I've had success with. Redundant ignites and using both Roshi and Sage Naruto's mysteries in round 2 go a long way. I use 3 2 3 2 2 dog of hell and put all of my best gear on roshi. Tobi's mystery with the poison tai talent can do a solid 5k damage if you use it after their heal standards, and his chase ignites early in your combo to prevent a lot of Sakura's healing. His chase also continues dishing out damage to Roshi in late rounds.

Arena is a completely different meta due to the relative differences in damage and life.

lets say in arena roshi's chase do a ton of damage while outside arena, due to how resistance scales it down, the chase is mostly there to spread again ignition, and while in arena you heal 1789/1944 with mystery and ignition lands around 1500-1900 damage on ninjas that own 9-11k hp, outside arena ignition lands the same 1500-1900 damage while enemy mysteries heal 4-5-6k and your hp are way higher... So in arena you can't let ignition go off while outside arena you just let the round end, ignition do the damage and then you heal back fully.

Came across it in spacetime so I thought I'd post the results here. This is 82200 power vs 83900 power, with all of my best gear stacked on roshi (even to the extent of having some life magatamas and initiative runestones on roshi be 2 levels higher than those on tobi)

That's an auto battle, the ai is so * there to use both sakura and main healing the same round, even if in round 2 one single ninja lost just 1 hp, is not weird that you won.