Burning Earth would destroy this deck with the amount of shock lands you're running... Not just that, but serious burn decks would destroy or outrun your slivers, because you can't counter all the burn spells. Most good aggros will have you beat by turn 4 if they go first, because you won't have enough mana to advance your own field while slowing your opponent's.

For example, I go first and play a Rakdos Cackler . You go next, shock for a breeding pool, and play a galerider. I go next and play madcap skills and do 5 to you, so by t2 you're at 13 already. You go next and shock for a hallowed fountain(11) and play another galerider, saving for a fog and attack for 1. I go next, play shock and kill one of your dudes, and boros charm your face (7) and attack with the cackler, you fog... you barely got 2 lands out and you're already at 7. See where this is going? T4 or 5, you're done.

The only way to do slivers right is to use red slivers or things that speed up your game and ramp, like an elvish mystic.

Aside from all that, burn decks are inexpensive compared to this, which means that any old pauper with a burn deck could outrun this.

Yeah I just played my actual sliver deck (which is the poor man's version of this) and the reds in it make it way faster so I'm just gonna re-do the whole thing haha