This is pretty simple, quick and easy for good XP dependant on your area. As you know your save points heal you on every single use so if you're in a good spot with a lot of monsters/mobs(Also Mini bosses such as Skeletal Champions) around then it's ideal.
Steps: 1. Kill the remaining 2. Go back to your save point and save. 3. Go back to Main Menu 3. Reload your game, and the monsters are respawned.
Simple? I thought so. (This Does Not Include Main Bosses)