I played a bit (over five hours,) of Destiny recently. It did not endear itself to me for a number of reasons, but one thing in particular stuck out. Around level six or seven, the level of the story missions suddenly jumps up a few levels. "Alright," I thought, "I'll just play some crucible then grind a little in that patrol mission." So I stumbled around in versus, feeling wildly confused and outgunned, then did four or five nearly-identical "kill these things you've been killing forever and pick up the things they drop" quests.
It all felt... empty. The patrol mission felt like a fat lot of nothing happening. Crucible felt like it was stacked against me, if only because I felt like I lacked any sort of meaningful loadout choices. I've dug into this a few minutes, and it looks like I could have been missing any number of weapon attachments or non-scaling stat-bonuses because I simply hadn't found any rare weapons. Or not! It's not entirely clear. This is a problem Destiny has in spades, but it's beside the point.
Grinding through the non-story missions is a chore. You're allowed to have non-story missions, and they're allowed to be fun! They're also allowed to be rewarding. Like, with actual rewards in the form of items I might be able to use. Borderlands showed us that, and it's in roughly the same genre as Destiny. It's just that progression seems to rocket forward in Borderlands, and that keeps things novel.
I dunno, maybe the grinding phase fades away after the five hour mark. And maybe difficulty increases by doing more than adding health. I'll probably never find out. If anything, I'll probably go back to Titanfall and pretend it's Metal Warriors.