Economy 101: Bioware has a finite budget that it can allocate to the development of ME:A, every penny that is swapped to the development of MP is a penny less that is allocated to add depth to the story, if the budget shrinks, they need to cut corners somewhere, adding some improvement to MP almost surely will mean cutting out a Single Player mission that perhaps would have been a wonderful addition to the story. If there were no other games around where your character can pick a gun and give you the enjoyment to make the life of other players miserable, I would understand, but is not the case, there are thousands, even if you're a EA fan, go and play Battlefront. Mass Effect main strength, its main selling point ALWAYS was the story, not the MP.
Ah! I forgot, an example! http://forum.bioware...the-mp-bioware/
There you have it...
I don't presume to know how EA does budgets. At least for ME3, the MP and SP were developed by completely different studios (SP was done in Edmonton, MP was done in Montreal) so there was very little - if any - budget overlap. But again, I don't know how EA is budgeting things this time around, so I couldn't say anything substantiative about it.
As for the example you linked, allow me to let you in on a little secret: OP was trolling all the gullible SP players, and boy did it ever work