Just because he jumps through fire, doesn't mean he's bending or anything. You don't just catch on fire if you run through it. You know how if you hold a candle wick against a flame, and it takes a few seconds to light? Same thing with Amon. His clothes were probably designed not to catch fire easily- he has to carry those electric things with him, right?- and he's agile enough to just jump through it quickly without getting burned.
Tarrlok said something around the lines that Noatak could have used subtle bloodbending to slow down his opponents, or move their hands or movements so when they attacked him with an element, it would just briefly miss.
But in this case, all I can come up with his his agility. He moves very quickly and he is also very durable- the man was able to stand on his feet again after being electrocuted by lightning, merely a few minutes later- but I don't think Mako's lightning is quite as powerful as a master's. ..When I saw the scene with Noatak and the fire, it almost looked like it moved out of the way for him- like he was in a bubble. Maybe his psychic abilities stretch beyond waterbending for all we know?
amon probably knew that he would get attacked by a lot of the elemnts before he started the revoulotion so he probly he made armor that negated the effects of a lot of the elements plus he really agile and somebody try to tell me he doesnt look awsome