Too many people

And yet they all look the same.

Well, it is a migration/colonization effort. I don't think the species representation is that far fetched.

The Arks carry 20,000 people each. This is explicitly stated. I'm not sure how many were on the Nexus, but I think that was also around 20,000. So 100,000 total approximately.

Yeah - I seem to remember 20,000 per ark in the diaglogue. I was going off what it said in the wiki - someone must have got it wrong. But whatever, nowhere near 800,000.

Well, there must have been a secret ark of criminals (unknown population)

The impression I get from the story with the Nexus and exiles, was they didn't have a lot of people out of cryo, yet there's a large enough population of Krogan to start a colony, lots of crooks, bandits and pirates where ever you go in Heleus. Supposedly we've got the Krogan genophage that keeps their population down and supposedly humans under some form of birth control.

I don't recall seeing how many were aboard the Nexus, but the Nexus survivors seemed stuck with keeping the population low because of low resources.

You need serious funds to pull that off. Unfortunately, not every race had it and this is pretty much a last-ditch effort to get some species to survive a very possible catastrophic and genocidal win by the Reapers. I'm just surprised the Volus didn't make it onto a ship because they're big-time money handlers.

Another example of poor writing.

1) by the Andromeda Initiative start (~75?) and Ark launch (85)... Quarians were considered squatter and vagabonds of the galaxy, no idea why anyone would give them an invitation to the Andromeda Initiative
2) why put the unstable, aggressive Krogan onto the Nexus?? Maybe to have some ground troops security? But then again, they got turians too...
3) Turians... THE most uptight and disciplined race in the galaxy, sure there are "bad" ones... but noone would put anyone with a "criminal" mindset on your forward station going far far away
4) Why is all the tech (Nexus, Arks, Outposts) of human design? Even all the shuttles are human. I can see why the other major races (Asari, Salarian, Turian) are part of the AI, but why arent their arks of their own race design? (Yah yah sure, anything can be justified, especialy this, like they had no time to design 4 different arks, but hey, we got 4 races working on this... look at the Normandy or Tempest, it does not look like the typical humantech, so we could expect the nexus and the arks to be of mixed design, whatever.)
5) And last but not least... this "numbers" are bugging me. Like Laughing Crow said, there were actualy not that many people out of cryo before the Nexus uprising. But there are human/turian/asari outlaws everywhere in large numbers... (just checking the stats, 980 outlaws killed..., at this rate, the human population will be decimaded by the end of my game)

This whole uprising makes no sense, if you are going to send someone ahead of the arks to serve as a forward operation base, you are going to hire only extremely reliable, disciplined people who keep their bearings together, no matter how badly south things go.

Boom! Goes Garrus' sniper rifle... head shot.

However, there is a counterpoint to this: Every colonization effort, historically from an Earthly view, was usually done by adventurers, desperadoes, indentured servants, etc. I can't remember who said it here, but you're not going to send the very best to sacrifice everything they love on a risk. The people that you will get are ready for a new life and who knows what is motivating them. Though, N7 knew about the initiative and would've had to go through their ranks to find suitable candidates, you can't tell the quality of the soldier going. It could be used as an excuse to get a team member that wasn't performing in their unit. It's a crap shoot at best and whoever you are... you're right. 

Oh, there's no doubt serious money is being spent here. There's, what, the Nexus, four arks, supplies and cryo stasis pods to account for? And that's just a big ticket list.

I'm guessing that there are Volus, maybe, on the last ark. I hope so, anyway. It'd be a boring universe without them.

BOOM! Goes the Common Sense Laser Pointer...

You want to lead from the front, not from the back... unless you're a Turian Naval Commander, then it all makes sense.

Why not Alec and the Ryders?  He has the most advanced SAM, he has been working with Garsen the whole time, you would think Alec would be among the first to arrive.

But, there are plot holes throughout the game big enough to fly the Hyperion through.  The one that bugs me the most is the exiles have been on Kadara for about a year.  An ANGARAN planet.  Yet both species pretend they never saw each other until you show up on Aya.  Why, on arriving at the Nexus, dont you get briefed on them and the Kett?  

Ultimately, to enjoy the game, you just have to treat it like a third person shooter, and the story is just for setting.  A shame, since story telling used to be the strong suit.