I'm sharing this from my group experience in my server(554)

in Matsuri, all my group mate gave up, the battle is so unbelievable hard, one of my friend are level 75 with 22k power, on his 3 first battle he said he battle a person with 31k power on level 78, 29k power on level 74, and he fight a person with 25k power on level 69, me myself on the first 2 battle in Matsuri lost 7 ninja, and currently didn't have any revive potion to try again, lose the first one and then i won in the second one with a bit of luck I guess, anyway atm I was level 72 with 24k power, my first battle are with a level 78 person with 28k power (but on a superior ninja, wind main with sage naruto, gara kazekage, and AO, LOL I can't even kill the bunshin of naruto hahaha). My other group mate have similiar condition in Matsuri, where they will lose the first and/or the second battle easily, maybe the opponent searching method not based on level but also power, so there some chance for a fight, just my opinion.

in Arena, training battle was hell, I don't know why people are there using their main formation over and over again ( I met this person 4 times in a row, so I guess he didn't fight for arena mission like me). Since arena point are only obtain for doing arena mission and using first time win on newest ninja, claim victory is though with a limitation of Ninja, I try to say that in a new release server normal player in average will have 30-50 ninja, my server are 2 month old, and the rank 15 in "Ninja" have only 50 ninja, which make hard to make a combination for a new player on new server to win here. Well, like how about player with 30 ninja or so, they will absolutely skip Arena. Not to mention that in Arena the speed are limited to x1, while all the Ninja are level 100 not awaken, and I didn't see the retreat *on, make Arena take a long time only to see the "defeat" interface lol. Here I recommend maybe make only the rank battle cross server, while the training lone server, or maybe after 60 sec that player didn't get enemy in his own server, then the system will get him an enemy from other server.

It just an opinion though, and I'm sharing mine and my group mate experiences.
Thanks!