i don't think two face is dead, either it was bad acting or he wasn't dead because i saw two face breathing while on the ground
i think you're just seeing things. i saw it 4 times and never noticed him breathing, this last time i specifically watched for something like that because people were saying he could still be alive. plus at the end they are doing that whole memorial speech for him when batman goes on the run and gordon breaks the light.
i suppose anything is possible, but i'm pretty sure he's dead.