First of all, the animation looks smooth (the walk-cycle in particular), especially in comparison to some of your other movies. The font in the different areas was creative and fit in well; the light change around your studio name, the studded text during the trailer, and the stars coming from either side of the title at the end. Unfortunately, there seemed to be some slight lighting change; not really flickering, but in different scenes, the amount of light seemed to change. Of course this could have been intentional in some areas; such as the poles coming from the ground, or the side of the arena that they are on. The text in-between the scenes made the light change significantly less noticeable.
Now as to how it appeared as a trailer. I noticed that you never showed the attack with the outcome; you showed both of them, but at different times. Consequently, one becomes interested in the outcome of each attack. Also, as Daniel pointed out, the battle did become more intense as it continued.
The trailer is well done, showing the main point of your film, and what is necessary to grab the interest of the viewer, keeping the best for the complete film.