Just go into this game recently, so I thought that I would share how I was finally able to defeat this boss after many frustrating failures.
The secret for me turned out to be using Aural Decoy as soon as I walked in. I cast it to the right, and this distracted the enemies enough for me to slip past to the left. I could then take out the dogs while they were focused on my decoy. After killing the dogs, circling the Demon and blocking his attacks did the trick for me.