I just read The Final Hours of Mass Effect 3, that app by Geoff Keighley. Great read, it goes into a lot of details from the very start of the franchise back in 2003. Codename SFX was the name of the game in early development (WIP name) and Casey Hudson was the one to actually come up with the idea of ME games and he approached the Docs with it and they liked it. Really great read. Also, I can now see why the ending was this crappy and why the game is full of some weird bugs, it's because it was the biggest game in the franchise but it had the shortest development cycle. Casey said that the team was really on the edge because of it, and the only delay they got was from Dec 2011 to March 2012 which was still not enough. Because of this, Palaven mission was cut from the game(We were also suppose to go to Turian homeworld, not just their moon) and some other stuff. So, eventually, I don't think the full blame is on BioWare, majority should probably lie in EA's hands. They are the ones who wanted the game out in an extremely short period of time (The original development time for ME3 was LESS than 2 years!!)
The development of ME3 was at least more than 2 years, because it was being worked on even before ME2's release, and ME2 released January of 2010, and ME3 March of 2012, 26 months plus a little more.