The Nether, I've found, actually feels like it needs a considerable boost in difficulty. Just because I was impatient, I created an inventory-edited world separate from my main world and went in to the Nether with only an iron chest plate, an iron sword, an iron pick and a bow with 99 arrows and I was able to survive in the Nether for about two weeks just by ducking the Ghasts, building temporary Netherrack shelters and hunting isolated Pigmen for their tasty bacon. On Hard difficulty, mind you!