Of course V was the main character. He/she was the title character for goodness sake and had just as much screen time as Evey. As important as she was, the whole film was about Evey discovering V, she was the audience's POV into the world.
As for Batman, I'm pretty sure in most of the films, Bats had at least as much screen time as Bruce and I don't think I've heard anyone say "I'm sick of that freak in the mask, I want more of that smarmy rich bloke!"
But if you want a more relevant example, how about the most glaringly obvious; Vader. Sure the films don't follow him around all the time but he had several rather powerfully emotional scenes across 3 films and the mask (which showed nothing of the actor's face) to say nothing of his voice being dubbed after the fact was never an impediment to realising the character.
All you're really missing with Dredd is the eyes and a skilled character actor would still has plenty to work with. Hell, Levar Burton managed to get along with a hairclip covering his eyes for seven years and it didn't stop him from effectively portraying an engaging character.