Involving more than one office is not really the definition of a line wide crossover though, and neither is the non-participation of some volumes. Involving multiple editorial teams is a good way to increase the reach and scope of a crossover but no one would claim that Original Sin was anywhere near the scope of AvX.
Age of Ultron confused everyone because it was wide in scope but ignored by many books. Again if everyone stopped listening to the hype it would have been obvious that it wasn't a major event. There is a clear schedule of major events every two to three years. They have a big status quo changing event and set the major lines on a track, then once those major lines begin to run out of steam they bring in the next big event.
Reading this back before I submit this sounds a bit cynical but I am not. The Event structure works really well at the moment, and let's face it you can't market an event by saying "this event only has limited scope, and doesn't change too much".