To be honest this trailer was the worst to me. Nothing special. I dont really like the comedic feel of it. I kinda miss the old DOA levels. Also it seems that the non ninja fighters have generic power blows.
They kind of do, yea. Most of them are recycled between older moves strung toghether in a stylish fashion. I think the idea was that it gives the player a "free" auto-combo with major environmental assistance and thats what they wanted to emphasize.
First I thought this was just more special treatment for the ninjas. Thinking about it more though, it seems like it was just really hard to do for the ninjas in the general. They don't have any real-life counterparts to base their in-game styles off of, so making their moves work in a cinematic fashion is difficult.
Hayate didn't really have much in the way of long strings that "flowed" with the level of power they wanted displayed cinematically, so he got something new entirely. Running up and thumping his enemy in the chest with a bunch of mid punches doesn't look send the right signal.... nor do any of his strings, really. They just took advantage of the blurry ghost-model effect and made it look good. Very little work, very good outcome.
Hayabusa's moves frankly don't even look like real attacks, and the way they impact would look silly if they tried to emphasize each hit in slow motion with a cinematic camera. The obvious solution was, of course, fireball. They already had the animation work done, and had the cinematic angle perfected from his DOA 4 ending.
Ayane actually sort of breaks the rule. She is using attacks she actually has and makes it look good by injecting abilities she does not have, which is the teleport. This extends her spinning nonsense and makes it look physically reasonable to have caused more pain than usual.
Kasumi has a whole bunch of new moves and I think they used at least one for her powerblow. It does end with her charged elbow though, so that is borrowed as well.
Just my take on it, at least.