You grind for better rolls. Better rolls = more power and flexibility in gameplay. Do you have an Enhanced Bomber + Enhanced Ashes + Enhanced Momentum transfer set? Have you tried stacking it with 5 paragon mods? 5 Ordnance mods? There's a hundred different builds you can grind that believe it or not have a massive impact on how powerful you feel. I can agree that there's a lack of content to test your power on, but I think the different iterations of the Forest are exploring options to take hordemode in a Diablo-esque direction, which would actually be really cool for Destiny.