You're level 35 trying to get the highest rank in arena... Gaara's stats aren't that great and he can be interrupted before his barrier gets put up. Standard attacks can bring him down easily.

I'll agree that 9-Tail Naruto is a bit cheesy in arena, as well as Iruka, but trust me there are a lot worse things. Like Water mains with their kiba poison or any sound ninja + Kabuto lineups, where you'll literally chip at Kidomaru's HP.

It takes less than a week to hit 35, isn't that a bit TOO early to be judging the game's balance? You'll find out once you hit 50, that those characters are basically irrelevant (except Gaara is still okayish in ranked battle, and Iruka is amazing). Actually ranked battle is where the P2W shines, since it's about the OP ninjas everyone has.

You don't even have access to all your skills yet, as well as all the free ninjas you get later on.