I'm in the "lungs were burned badly" crowd. I never had a problem understanding the life support suit. As previously stated, the issue does come up of why Anakin and Obi-Wan weren't completely fried shortly into the battle, but all Lucasisms aside, I can actually buy that they were using the force to protect themselves, along with the shields on the miner droid/platform. Anakin gets 3 limbs cut off, goes into shock, his focus drops, and he goes up in flames. Seems pretty straightforward to me. It would be fun to see more of Vader being badass, instead of mopey and depressed. He should use his anger for his own power, not stand there and cry in despair. Lucas may have had the general right idea, but somewhere between his mind and the screen things got more than a little muddled.