I disagree. The Demise battle was one of my favorite ending battles of all Zelda games.
I do not think it was the hardest battle ever, but it wasn't the easiest. If you used guardian potions and health potions i'm sure it was much easier, but i didn't use any potions, because i wanted the full effect. Did you use potions? I did think it could have been a little harder, but for me it wasn't to the point where it was disappointingly simple.