[Kewing]

I was in the same dilemma recently, so I started going the way you described. However it's still unclear. The way I see it, that's a good approach if the arranger has made significant changes to make the song sound quite different from the original composition (like in remixes), but what if the arranger's role was not that noticeable (like when arranging music for a port of game e.g. Raiden AC -> Raiden PSX) and it sounds basically the same but with better instrumentation?
And yet another one: what if you have a performer, arranger and composer, all different persons?
I think I would ignore the arranger if his role wasn't that big. But I still don't know what I'd do otherwise.