User blog comment:Ygrain/Leviathan: Do you know what you are doing, Bioware?/@comment-4950455-20120906232557

Leviathan did open up a few plotholes, although probably not as many as it closed. However, I think you're wrong about this being vital information that was "made" into a DLC - my guess is that Leviathan at least partially exists because of the complaints of how poorly (or not at all) the Catalyst was foreshadowed.

Should this information, or something equivalent to it, have been in ME3 from the start? I can't say "yes" strongly enough. But that's not really reason to condemn Leviathan itself.

Also:

''Frankly, the information you're presented with in the Leviathan DLC gives a lot of factors that would have influenced the civilization that eventually felt that organic/synthetic conflict was inevitable. If anything, it gives more credence to the idea that the views of the Catalyst and its creators were flawed.''

I really have to second this. Finding out exactly what the race that created the Catalyst was like did more then anything else could have to "redeem" it in my eyes. I certainly don't buy its arguments, and I wouldn't have ever written in something like it myself, but it's no longer the "yo, dawg, I heard you were having problems with being killed by synthetics..." joke that it was in the original endings.

And, incidentally, I'm now considering choosing Synthesis in my next playthrough - despite my many lingering moral issues with it - for the sole purpose of spiting all of the people who complain about players being "pressured" into it. Nothing in Leviathan provides additional support to any ending choice.