Yes
Baines benefits massively from having Pienaar in the side - whenever Pienaar and Mirallas switch flanks, Baines becomes less effective. Given that the majority of the chances we create come directly from Baines, having Pienaar back is a good thing.
Personally I don't think either he or Baines have been in anything like the form they were in pre-Christmas since the turn of the year. Perhaps one is to blame more than the other? I don't know, but what I do know is that we are a better side with Pienaar in it - the times we didn't have him last season should illustrate this. We probably paid marginally over the odds for Pienaar but then we knew that we were getting a sure thing as far as his relationship with Baines is concerned. Taking a chance on someone else would have been a gamble.
Oviedo isn't even half the player Pienaar is btw, and he runs into the same areas that Baines does, again making Baines less effective.