So, yeah, they use the same assets as the multiplayer mode but when I first heard him complaining, I had also assumed that you'd be performing the same tasks (wave survival, point defence and activating beacons) when, in fact, you're doing vastly different tasks with a strongly intertwined narrative (although not particularly 'important' within the grand scheme of things) and the missions themselves don't take too long. They play out very differently from the co-op stuff due to the team-mates you can order around and the fact that the objectives make different use of the space.
Sure, it's still weird that Shepard overhears so many things in the Citadel and goes out of his way to fulfill every minor inconvenience, but it's no weirder than every protagonist of every RPG ever feeling the need to walk into people's houses uninvited and talk to every single person out of the blue as if the entire universe revolved solely around them.
Am I missing something or does anyone else feel the same? I'm about 19 hours in, feel like I've pretty much done most of the main stuff and have loved the game so far, a great deal more so than I was initially expecting, especially considering all the negative talk on the Bombcast.
EDIT: Should have specified that I meant the N-7 missions mainly. I agree that the scan and deliver fetch quests are awful and dull in the worst way, especially as the quest log does an awful job of tracking that. Then again, I never felt obliged to do any of those as my Readiness rating was so high due to all the co-op I played. I don't think that the Shepard as a creepy sociopath argument is valid though - every RPG has you randomly butting into people's lives in some way after all... It's a genre convention and how those side quests are delivered doesn't matter that much to be honest.