I bought the game a few days ago and I have to say, I like it a lot, specially the fact you can choose which skills a demon gets when you fuse it. What I mean by that is that unlike in Strange Journey you can choose what skills are inherited and unlike Devil Survivor you can remove the demon's default skills if you don't like them.
Right now I'm lvl37, and honestly I'm having no difficulty with anything that isn't a boss, then again I'm probably over leveled and using a DLC set of armor that hasn't been equaled by other gear although they're starting to catch up. As for my demons I'm using Nymph Kikuri-Hime, Jirae Titan and Femme Medusa. And since I like showing my stats in games like these here's how I'm set up right now.
Samurai Ryoma
Lv37
HP:476
MP:222
St:67
Dx:55+9
Ma:7+9
Ag:55+7
Lu:55+5
Sword:Luna Knife
Gun:CC Rifle
Bullet:Steel Rounds
Armor:Demon's Skin Set (A DLC set of armor that can be obtained in exchange for 10 Life Stones per armor piece.)
Acc:Company Earring
And Feathers, the fairy that killed you was a Napaea, and yeah, skills in this game hurt a lot, heck even at level 37 I can actually take quite a bit of damage from weak enemies...But only when they ambush me because I one-shot most demons around my level with Javelin Rain, a phys attack that strikes all foes for "medium" damage.
Finally a little story that proves that even low lvl enemies can be devastating: I was going about my business as usual until I get ambushed by two lvl9 harpies, the little buggers each used Mazan and since I'm weak to wind they each got an additional Press Turn Icon, which they used to cast Mazan another two times, after that I had 2 demons dead while me and my other demon with 1 digit HP left. And that reminds me, one thing I just love in this game is that you only get a Game Over when your team is wiped out, meaning your character can actually get KOed while the demons continue fighting.