I definitely think there are a few things I could change in marathon training to improve for next time, but I'm not necessarily sure "harder training" is the thing.
Maybe I'm wrong there, but I think I could do with a touch more volume in my marathon specific workouts. However, I think the intensity of those workouts was spot on: I basically ran the exact same pace in the race (with the same HR figures) as I ran in those workouts (if you take out the big hill at 36k).
I'm also aware of plenty of guys who ran over the weekend, who did much harder workouts in their prep than me, who faded much worse than I did in the last 7k of their marathon. Obviously, there's plenty of other variables there - but I think making marathon workouts too hard is one of the biggest mistakes people make in marathon training. Again, I could be wrong there, but it's certainly a mistake I've made in the past.
In terms of easy running, I'm aware that they probably look very slow to other people, but they don't feel that slow to me. I'm blown away that other people with similar times (or slower) can bang out 7 minute miles for their "easy" runs. To me, that just wouldn't be easy at all. And I wouldn't be able to run 90 mile weeks if I did that (I doubt I'd be able to even run 60mpw). But if people can get away with it, and they think it's working, then more power to them.