I like the double melee charge. But thats the only thing i see useful from that item. Obsidian mind has increased grenade throw distance and more super energy from minion kills. Plus the nova bomb perk. The first part of the new raid, when you run voidwalker with obsidian mind, you can run your super in less than 30 seconds each time if you do it right. You can wipe out entire mobs, generate 8 orbs for your teammates and be ready to go with your super again. I love sunsinger but voidwalker is a lot more fun.