How many truly hard bosses have their been in a 3D Zelda? The blight's just exist to add closure to a beast and move the main quest along, they aren't really there to act as a gate to progression anymore. That job now belongs to the map and all the systems that interact with it be it enemy placement, weather, stamina, weapon durability and on and on.
I'm really excited to see how Nintendo goes forward and I would be fine if that didn't include traditional dungeons.
The blights are tough only insofar as the game's combat is tougher. Got OHKO'd a couple times by thunderblight Ganon, which is more than any Zelda boss has done to me in a long time (at least outside of the NES games that i played recently). Mechanically they're much less complex, though still similar to other 3D Zelda bosses in that there's one trick to beat their respective special attacks, which is item-based.