You can also split the mana between two different creatures to give multiple cards haste in one turn
That being said, the default deck list is absolutely fine for casual play, and very straightforward and fun to use, so a top-half position for this deck feels fair
In black, using Bargain should be easy to make Candy Grapple an all-star removal card that can hit nearly any creature in the deck aside from massive finishers in green like Hamlet Glutton
Eris also has flying and prowess, but the most important thing is: Once it's on the battlefield, whenever you cast your second spell each turn, it creates a 4/4 red Dragon Elemental token with flying and prowess
It That Betrays As if annihilator wasnt hated enough, It That Betrays powers it up into another hated mechanic, allowing you to steal the stuff that your opponent sacrifices
That said, while Altar may be limited by the assassin creature type, there are very good ones in Mardu colors, like Vein Ripper or Thorn of the Black Rose, that can impact the flow of the game