OK, I know what you're going to say, it all goes to custom as soon as you make one change..... BUT!
I think that if you start on Legend the overall game play is better. I was having trouble getting good gameplay to fit me. I'm an older gamer who plays Baseball games a LOT, but for the football games I'm somewhere between a casual gamer and a full out hardcore footballer like some of you guys.
I started using as many sliders as I could find with varying results. Then I tried Ricksters fair play sliders. and even though every lots of things were maxed, it was a good tight game. I played several games and there were all good. So I started to try and see a difference. The difference was, he started on Legend. I tried some other sliders and started from Legend. I tried some of the ones that were started from All-Pro, and based them from Legend. Gameplay was much better.
I think the DB's aren't as dumb. The OL/DL plays better. It's much tougher to make passes. Seems the overall play is much better. I don't know how, or what or why, but it seems that way.
My request, try it. Take the sliders you like, and start them from Legend, and see if you get any better gameplay? Or is it all in my head?