There is a tier list, but it's quite outdated and old that dates back from DOA5U.
http://www.freestepdodge.com/threads/the-official-tier-list-with-discussion-thread.3817/
It could use some work to include the missing characters such as Naotora and Mai. DOA is one of the games where the entire roster (with the exception of Alpha) have access to a hold system that can provide reversals even to the worse characters with proper reads and fundamentals applied. Honestly, I find DOA to be pretty hard to determine to make tiers when they have access to this, as well as too many information that comes from their own personal approach and experience that may vary between different players, skill gap is involved that makes it difficult to determine proper tier placing.
Ex: Ein is one of those characters that's considered mid or lower (even Naotora) but once those characters provide tons of reads with holds or throwing opponents, they can practically win matches just by playing like that which makes tiers something to not truly care for if they have access to unbreakable throws (not neutral throws) and getting proper holds in. Course, it has tiers, but it's not a heavy mess like an Injustice game or Marvel.