The problem with putting typical sources of card draw in an aggro deck is that it distracts from your main game plan, which is to play creatures quickly and attack
On top of a sweeping +1/+1 counter effect, Fluttershy can take a key creature out of the equation, so long as you're able to keep your eyes on it
At the low cost of one generic, one blue, you could very quickly build an army of Persistent Petitioners
Mirran Crusader Mirran Crusader is a classic double striker with okay stats and good creature types
Similarly, there were also asks to depict the zombies of Innistrad and the faeries of Eldraine
Last, but certainly not least, we have Invasion of Tarkir