people who say the game is too easy almost 99.9% of the time have no proof that they played the game on higher difficulty levels
Well, it is. Kind of... It all depends how you play. For me, DMD was easy for the most part because I took full advantage of my moves and the levels. There were a few enemies that killed me here and there since I didn't have a good plan for them, and my best strategy ended up being to demon dodge and attack them whenever they were open.
But.... it's very difficult if you try going for style. Kind of like DMC1, you as the player can choose how to play... and this will make the game more or less difficult.
Hell, even the bosses can be both easy or hard. The only reason the bosses in DmC are 10 times easier than in DMC1 is that they actually give you a weakness to abuse. Mundus's spawn for example... at first I just tried parrying his attacks, and fighting him like Succubus. I ended up dying like 5+ times on Nephilm. However, when I went after his arm, and his eye... I ended up killing him my first try. Then later on DMD I found out that you could abuse his weakness further, and if you Angel Lift his eye then he'll fall on his butt and allow you to do serious damage.
Don't get me wrong, I LOVE that this game gives both enemies and bosses weaknesses. I absolutely love it. To me, a game should never force a player to play on a higher difficulty than he wants (Super Costumes can force some players to play on DMD). DMC1, DMC3, and DmC all give the player tools to cater the difficulty to their needs. I've only beaten DMC4 once, so I'm ignoring that.
DMC1 gave certain enemies weaknesses to abuse, and it also gave 5 untouchables per playthrough to players like me who wanted to have an easier time against bosses.
DMC3 was hard... and arguably annoying... but they gave us a cheat code to instantly unlock everything, and with the super costumes the player could once again cater the difficulty (excluding the HD collection... they screwed up that game due to disabling the save/load).
DmC, no different. Instead of untouchables, the bosses are given weaknesses to abuse. The enemies aren't as easy as DMC1 since their weaknesses are limited to stunning them instead of utterly destroying them... but hey, that's why there's demon dodge.