I played 10 duels (not enough, 8()), and I didn't feel any inconvenience due to the small field size. The "fat" units either move first and have ranged attack or flight, or they rarely appear but have a buff or an ability that allows them to say something. The only exception is Hydra. It seems she should stand like a statue in defense. This is my impression so far (I mainly played against Jhevon):
Here is a topic with screenshots from the beta; it contains many images from all over the world ;) - /topic/173/