The main focus always has to be SP as long as you're not developing an online only game. And in this type of game, Coop then comes next as it's almost automatic once you have SP.
Other MP modes are always implemented at a level that depends on the time given.
GRAW's almost complete lack of MP "implementation" at release allowed it to turn into the success it is today
I would hope they would learn from such an obvious mistake the second time around.
It has good MP implementation for a TFPS. The MP Coop works great. Like said, everything else isn't what is essential for TFPS.
For any other genre other than a TFPS I might agree you can get away without a strong multiplayer element.
When GRAW first was released there was alot of excitement from the community. On any given day, dozens upon dozens of people would browse theses forums and the official forums. Now, I've regularily seen only 3 or 4 on in prime time. Is this a good guage of a games success? Not exactly, but its only mere months since release and there are less than 100 folks playing online on a regular basis.
First person shooters need MP just as much as single player, in my opinion they need it more to be successful and have longevity.
The larger bulk of the public which bought GRAW moved on before proper mulitplayer aspects were patched in. Even now, months later, patches later, it has a limited MP content.
In my opinion, the community wants a full MP at release so the game doesnt die a premature death. People nowadays have options when it comes to game buying.
If your only into co op play then maybe your satisfied, But the larger part of the community wants a game too that isnt on the shelf in 4 weeks. Other game creators could do it, why couldnt GRAW's?