In all honesty: I'm not sure I'm a big fan of the Stampede. I can see how it should usually come out great, however, it also feels like overkill. The point I want to cast this at is probably the point where it doesn't really matter anymore how I win. I'd probably play it if I could choose which creatures, but I don't have enough control over that. I don't like See the Unwritten for the same reasons as the Stampede.
I'm not a big fan of your buff fatties in general, though some are great for their protective capabilities (which I wouldn't call "buffing"). On the whole I don't think fatties need to become better at combat.
I like my sweepers to hit creatures first and foremost. I think you may have too few that do that.
I would play
Rings of Brightheart before most other shenenigans you include. I would also consider playing more man-lands for early defense and, just because you can, play a snow-covered version of every basic to be fully highlander.
Of course this is a reflection of how I and my group play. I am used to slower games, which leads to me aiming my deck at the late game. In a faster meta you either need to be hitting hard quicker or have the ability to slow others more. I'm not familiar enough with the online meta to tell you what to go for.
I know my personal taste would go towards slowing them down more, so what other early sweepers are there?
Nevinyrral's Disk?
Oblivion Stone?
Day of Judgment? How can I ensure that I have early blockers? (Man-lands, cheaper fatties) Or keep them from attacking? (
Dueling Grounds). If I delay them enough I should be able to start playing my game.
Of course that's my preference.