He's definitely easier than Venser. Lumen? Ehhhhhhhhh.
My biggest struggle with him is that it took me a lot longer than it should have to realize he punishes you for using anything that's not the Sword.
And I can see why there's some disagreement on difficulty: Tartaros is a lot more demanding on reflexes (mere rhythm will get you past this guy), but this is the only late-game boss (except the final one) that forces you to stick to your most risky weapon.
EDIT: GODDAMMIT HE HEALS IF YOU DO TOO.
EDIT 2: Allow me to update my analysis. This guy will be easier against people who play more defensively, strictly because healing or using Nayru's Love automatically makes him heal himself a lot. Tartaros hits a bit harder, but you're not doomed if you get hit more than twice during the entire battle.
EDIT 3: My reflexes are not fast enough for me to turn around when running to where he's going after a hit. Yes, this is pathetic. Yes, it is screwing me.
EDIT 4: Sure enough, I managed to win by abusing that blue-screen-flicker slowdown glitch that happens when I go full-screen. (I was unable to do even this against Tartaros, FWIW.) Now to see if I can do it without cheating. 
EDIT 5: Did it. Definitely easier than Tartaros if it only took me that long - heck, I think Medusa took longer. And then, of course, I accidentally walked back into his room trying to heal and almost died before I saved, lol.
Edited by Bill Nye the Russian Spy, 02 October 2015 - 12:38 AM.