Hard to say really. My morale dropped towards the end of the season as the team slumped to several losses (Only went to ~86 though), but there was no real correlation between that and any change in yards gained. And even if there was, it's hard to say what came first, the chicken or the egg?
Anyway, I can show you my FB, which I'd say is relatively balanced, but more geared towards blocking.
http://goallineblitz.com/game/player.pl?player_id=66867 (Will have it open for a couple of days)
Early on the high str (I got it to 45 very very early, and has only added a little since) was great for both blocking and breaking tackles, but as defenders caught up and put points into str/agi and skills like shed block it's gotten harder. I still block pretty well, but sometimes LBs shed my blocks and make a diving tackle on the ball carrier.
Vision is indeed very important, I noticed a significant improvement (Mainly in blocking) when I went from 22 to 28 or so. Next couple of levels I'll be putting points into blocking and vision, before maxing out strength.
However IMO it is very hard to build a good FB, because you need so many attributes. That goes for several positions of course; TE and Safeties spring to mind as well, but it's still true for FBs. Essentially you need the stats of a power HB but at least 20 extra points into blocking. And if you want to be a decent rusher you have two SA trees to put points into. However that's one of the reasons why I have two FBs and two TEs, simply because it's more of a challenge than many other positions. And because there are too few blocking TEs out there.