The gag with the 94 meetings with Ann was priceless. Stuff like that warrants her being around.
Mark can't really be compared to Jim anymore. Yeah, he's the obvious analogue, and they even go as far as to pair him up with NotKaren to really drive the point home. But his character is more about being stable than anything else.
Jim existed purely as comedic foil to everyone, but whose life goals have changed entirely. So at first he hates his job and has no issues about quitting, except for Pam. Then he decides he's going to stick around and attempt to climb the ladder a bit. Then he gets married and feels that he HAS to be there in order to provide for his family. This change has killed much of his character, since he now thinks he can't be as detached or goof around as much. It's part of whats diminished him entirely, being replaced with the kind of stuff that is counter The Office, where it's now this sort of "life works out" sap instead of Demotivational Poster.
Mark seems to have his job and somewhat like it, and really have no aspirations toward any extreme. Thinking about marriage to NotKaren struck me as out of place entirely since he's more even than S1/2 Jim was. It just felt like they'd dated, it was kind of nice, and then bam - hey I might propose. I think that element could be dropped, but his character needs to remain.
I just really dig the show. Knope has now eclipsed her hesitant Michael Scottism beginning into a full fledged character. Tom is hilarious. Emochick works and her giddy schoolgirl act with NotRoy is a great light happy element. NotRoy is hilarious. Ron is king. It's my highlight now.