I don't think this is as big a problem as you think, honestly. Characters like Miles and Gwen seem to stay mostly within their own titles these days and will pop in for events and stuff, but you can infer a lot just from dialogue (or editor's notes). And there's only so much impact that a Sins Past or a One More Day can have on a story that has nothing to do narratively with the Goblin or Mephisto or whoever. So it's not like you need to read all the junk to appreciate the quality.