I'm 12th on the power ranking on my server. Generally my 12th node is higher power and usually level than me - meaning top 11 ^^''. I clear the trial every day and about 85% of the time I have not a single ninja die. It's all about the formation and the RNG + Retreat spam until you get a favorable outcome. It's only worth killing off a squad if you're ABSOLUTELY SURE you cannot win and you want to sacrifice some pawns (meaning not your main 4) to kill off 1 or weaken the team overall.

A good tip is to keep ninjas like 9 tails chakra naruto, Karin, Shizune and Kankuro on your sides for the poison/ignition spread. It's a great way to weaken strong teams if the going gets dire.