Its just your biased opinion that hellfire is a bad zone. I quite enjoy leveling through the zone, as it is lore intensive. Its a nicely designed zone too. Its got that stark reddish landscape that really makes it feel alien and near to space. The sky looks amazing there too.
Blades edge isnt a bad zone either. It is varied and each little pocket is a new area with different and interesting quests. I admit, it was a pain to level through it during TBC when you didnt have flying until 70, but now that you can fly at 60, it makes the zone super fun. Try leveling there next time you are level 65ish, its not bad at all.