Rather than neverending mode (would be an option thou!). I'd rather have fixed waves. Something you can complete. Have you ever played Mass Effect 3's multiplayer? That had horde mode that had 12 waves. For every 3 waves, there would be an objective (transport bag to the marker, hack devices, escort AI drone that powers up via player omnitools, ect...) and the last wave was extraction wave. I think that was one of my favourite Horde modes ever. And if the challenge wasn't too great, you could always turn up the difficulty. The difficulty rises were rather sharp, but it was SO rewarding to get it right and make it to the end. This is something I'd love to see in Destiny.