I'm at a complete loss why anyone would think that a one hit kill difficulty is a mark of a deep combat systems.
Quoting from my previous post:
Going by the fact that there is a one hit kill difficulty and Platinum are great when designing action oriented systems, I want to believe that there will be deep mechanics on both action and rpg parts so that the hardcore can enjoy that difficulty mode without frustration.
I hope that by the simple existence of the mode it means that the mechanics are well thought and that this is a mode to test your skill instead of an exercise in frustration.
Platinum probably tested the game, including this mode, to hell and back so if it's in the final game it's because they are convinced they have a good combat to make use of it. It's something like Dante Must Die difficulty in DMC.
I certainly cannot say much more about the depth of combat because I haven't played the game yet. Those earlier gifs at least show some of the possibilities with the combat system and it shows a lot of freedom on how dispose enemies. If the game will make you use every system to its fullest or if you will only use them in higher difficulties remains to be seen.I wouldn't be surprised if the game is a simple ARPG for those that want that way but that contains enough depth for those that like DMC/Bayonetta kind of games.