That's why people use the league in most arguments. The NL, with weaker offenses and more spacious ballparks in general, always has several teams near the top of the BP chain, specially and the NL West, and it is inconsequential to the discussion. The Sox BP was one of the best in the AL last year, which is a stronger league than the NL, and the point can't be contended.
Also, if Aceves returns to the BP (likely) and the rotation gives them more innings (you mentioned Lackey but forgot the rest of the 5-innings and less crew conveniently) the BP has a chance for an overall similar performance, at least.