I think after the "Dave wanting more money" phase they felt the need to try to make all the original regulars know they were easily replaceable (odd since they haven't replaced Dave with a new agitator yet).
"The old vet who is just trying to make a good living" -- Ivy is there to show Darrell he can he replaced (although I think Ivy was originally meant to be the new Dave and fills some of both roles)
"The young couple trying to be the American Success Story (with wife with a great rack who makes fun of husband)" -- Am I talking about Brandi and Jarrod, or Rene and his wife???
"The comic relief" -- The twins as a sad low rent replacement for Barry.
"Man and Woman auctioneer team with the woman being sassy and having attitude" -- Which pair am I talking about?
"The agitator who is there for money and doesn't mind being the bad guy" -- This was Dave, and I think they wanted it to be Ivy, but Ivy just comes off a goofy and nice to much.
Show producers think in terms of formulas. They don't just want a hit show, they want a template they can make other shows from.