So I should take from Luke's claim that he does not believe one should (as a moral rule) maximise expected utility, or anything like that?

I probably shouldn't speak for Luke, but I'm guessing the answer to this is yes. If it isn't, then I don't understand how he's a particularist.

And that he would say that it's possible (if perhaps unlikely) for an action to be good even if it minimizes expected utility?

I don't see why he should be committed to this claim.