I actually found that Mei/Mabui/GNW Tenten/WaterMC was bad for Arena as you cna't just burst everyone as easily so I ended up swapping to Sage Naruto, Sailor Sakura, Killer Bee, WaterMC with Poison Tai/Neurotoxin. Works really well because if they don't focus Sakura she gets unkillable, and if they do focus here Sage Naruto kills them.