Bioshock 2 was the poster child for tacked on multiplayer that no one wanted.
I actually played BS2 multi up to level 20 or so. I will admit that I only got to play one or two modes, the little sister escort mode never had enough people for me to try it out. My thoughts are, the MP is too dated. Most of the weapons are hit scan and everyone has a lot of life, the levels are just your standard circular Quake affairs. Even with the skinner box leveling grafted on, its just too old school to be circle strafing and peppering people in this day and age, or tossing endless explosives.
Its spammy. Which is what the single player is built around, a sandbox for you to spam your arsenal on wilting waves of psychos. Its just one of those games that doesn't translate to deathmatch anymore.