True compared to the number of units sold the number of people complaining is small, however how many people would go to the effort to make that complaint, one only has to look at the official forums to see the vast number number of threads/posts that hate/dislike the ending for what is otherwise a great game.
Honestly i pity Bioware, and sadly i find it unlikely that they will fix the ending let alone release a free one. I imagine that Casey is likely using what you pointed out as validation. When it comes down to it though Mass effect 3 will be remembered but not as a great game rather as the game that had endings so bad that it tarnished an entire trilogy.
Donttttttttttttttt Skyheart will get mad. =[ One must not make Skyheart mad.