As people have said, difficulty wasn't ever the problem with NG3. Actually, the regular hard mode in NG3 is probably more difficult than any of the other games. It's just the wrong kind of difficulty.
You couldn't stock up on healing items at all, because there were no healing items. There were just waves and waves and waves of enemies with a ton of hit points, and it just got to be extremely tedious. You couldn't rely on ninpo, or even UTs. You had almost nothing to really help you through. You could easily get stuck at a checkpoint on a boss with 33% health, and you just had no way to heal, so you would have to restart the level.
Anyway, I really can't see how this one could be worse. The blood, extra weapons, extra characters, extra ninpo, weapon upgrading, and other extra content seems like a step up. Is it going to just amount to window dressing on top of a fundamentally broken game? Maybe. But I really don't want to hear anyone tell me it's worse without even a sentence of explanation why. Ninja Gaiden fans take the series seriously, and look at updates almost with the same eye for technical details that fighting game fans do. You don't drop in and say that the newest fighting game update is worse without even saying why. I remain skeptical.
Maybe the game won't fix anything, but even if its the same broken game plus extra content, that would technically be better than before.