"Lotto" is the first episode this season without Robert California and he's definitely not missed. The show works fine without him, better possibly. We don't have to deal with his ambiguous personality and motives and instead we get to see more of the characters already there. The cast is so large that there is plenty to explore between them without bringing in a new person.
Case in point, "Lotto" is a Darryl episode and Robert isn't in the episode nor should he. When his warehouse buddies win the lotto and quit their jobs, Darryl begins contemplating his life and future. His growing unhappiness culminates when he confronts Andy about not getting the manager job. Andy's serious and stern response, which differentiates him from Michael, is that Jo saw that Darryl slacked and didn't want him to be manager. None of the plot was particularly funny, but it brought meaning to everything going around the office and gave Darryl motivation to be more than he currently is.
The other plots-- Jim, Dwight, Erin, and Kevin at the warehouse, talk about how to spend lottery money--weren't that funny but weren't bad either. I don't really expect much from The Office subplots anymore, so they were fine, not annoying and with some bright spots.