I personally never understood why some people think ME2 was off point about fighting the reapers.

Probably several nests but also remember the scale of the planet. The asteroid that hit the Yucatan peninsula actually did very little direct damage. Assuming it was the kill shot that wiped out the dinos. The real killer was the after effects and as per linked in the article just because it hit a sweet spot to cause more damage.  Any nests situated in Florida or Brazil would have been left undamaged by the strike.

Equally the Rachnni are or at least were technological equals to the Asari and Salarians of the time. They would be just as equally capable of dropping massive asteroids from orbit.  So your idea of a quick easy fix would be instantly used against you. How ever as shown the Rachni would be able to survive on toxic planets that couldn't support races like Asari, Salarian or even Krogan. Given every reference has the word endure in regard to Krogan activity on Rachni worlds. 

One of the things I wondered is why didn't mordins team alter the genophage so it wouldn't be such a small amount of children. I mean they made it so you either cured the genophage or let the krogan race die. Mordin's team altered the genophage already so why didn't they make it 1 out of fifty survive or something like that. It would keep their obscenly high birth rate down without dooming the race. They would have hope and they wouldn't have the horde like they once did so they would have a chance to adapt and change into a productive member of the galaxy.

The lore of the collectors states that they like trading advance tech for livings beings. Request like 2 dozen left handed salarians, 16 sets of batarian twins, or there favorite human biotics have been made. It was obvious that ME2 was in fact going down the route of the dark energy theory. I believe the reapers were always controlling the collectors, after all they were repurposed protheans. Dark energy theory states that only organics could use dark energy, and using this dark energy could affect the space time continuum (which the player in ME2 witnessed with Haestrom's unstable sun)read a little about the DE theory here. Because the reapers were immortal, essentially, they were afraid what the organic usage of dark energy means for them. Eventually it would mean their deaths. So the reapers took it upon themselves to study the effects of organics usage of dark energy by harvesting and trading for them. The only thing I still don't get is the human-reaper and where does it fit in. But because the story didn't continue with the dark energy theory, we don't know. That's why I think ME2 story doesn't really fit in. It just has a lot of loose ends that ME3 didn't tie up because it didn't follow the DE theory. 

Yeah, I agree with you. Okeer also makes some odd statements about clutches and newborn dead and such. So it makes you wonder... it seems to fly in the face of the idea that females would be hung up on their babies being stillborn (from their eggs). Krogan should not have evolved to have much empathy for new borns... and I'd imagine their newborns would basically be animals who wouldn't develop a complex psychology until after a few months, after they've killed off most of their siblings, at the earliest. Perhaps in each clutch only a handful of hatch-lings actually survived to reach adolescence? How violent was the culture in general? Constant lethal tests of strength, intelligence, and toughness right up to adulthood? Sparta but on steroids, maybe.

Plopping the rachni down near krogan space might be a solution. I do wonder what the historical rachni were really like; all we get to see are savage, if clever, beasts. Presumably though they had a whole technological civilization so what might THAT have been like? How fast could they recreate one? The queen seems to have memories, if confused, from her ancestors so how much time would a reborn rachni civilization need to rebuild? They might be able to skip over a lot of development simply by having innate knowledge of their ancestors' long climb to high civilization, not to mention the capacity in the modern age to tap into the collective knowledge of the galaxy.

I do wonder, what is rachni psychology like? If krogan had to evolve to be aggressive and less empathetic then what about the rachni, insect-like beings who also seem to have hundreds of young at once? Newborns who are even weaponized fresh out of the egg, ready to kamikaze into an enemy and kill it. Don't think that I'm trying to paint the rachni in an unfavorable light, but how likely is that they'd really understand concepts like compassion or trust or even 'society' as we and other individualistic races do? It might not be inaccurate or a coincidence that in fiction alien bug races and alien machine races are portrayed as being fairly similar in their tendency to form collective hive minds and then mercilessly and dispassionately swarm the individualists around them.

I understand the theory but if that's the case how did they form a civilization at all? The thresher maws alone would have prevented any structures from standing. If they had found a way around thresher maws destroying what they had built then they could also have kept their children alive. Their history, in regard to physiology, doesn't make sense.

There is another possibility, which is that the krogan themselves were killing each other. We know they nuked the planet before they were ever uplifted by the salarians. Still, if their wars were big enough to kill off their children at an alarming rate, how did the buildings survive, even prior to the nuclear war?

It would make sense that the mutation occurred as a result of the nuclear war rather than before it. It only takes a relatively few number with this mutation to blossom into it being the standard.

I believe the codex on tuchanka explain alot about their world and just how difficult it was to survive.  Until gunpowder was invented the leading cause of death among krogan was being eaten. The krogan themselves have eyes that are positioned on their head like a deep or cow on earth rather then in the front like a human or a predator. The prey have the eyes facing to the sides so they can look for predators...the krogan have that and most would agree that the krogan are predators. That explains just how brutal their world is.

You know I just thought of something interesting. Why didn't some of the female krogan go on birth control? I can't imagine them have eggs and constantly being mothers was fun when they had so many.