Drawing a card each time a creature with power 4 or greater enters the battlefield is miserable for your opponents because they have to deal with what you have now and the cards you draw later
You regularly see an opponent tutor for a card during his or her turn but not have the mana to use it, so the player passes the turn
So much so, in fact, that its price seems to be rather low right now
Consider everything she facilitates: Freedom of play on your turn An ungodly amount of creature and artifact enter-the-battlefield triggers (and, likely, leave-the-battlefield triggers) An equally ungodly number of bodies to send to battle or sacrifice to the altar of your choice or tap to pay for convoke costs (consider that Throne of the God Pharaoh regularly loses opponents 10+ life at each of my end steps, if it doesnt just end the game) Offense and defense, as this deck can send everything it has every single turn, with Myrel creating untapped replacements for every single soldier you have Ample low-mana value, low power/toughness creatures to trigger all of whites card draw effects If a commander were printed that read: protect your board and make an army, such a commander would be considered a playtest card for White: the Commander

Doctor's companion (You can have two commanders if the other is the Doctor.) If Donna is paired with another creature and they are both dealt damage at the same time, the second ability triggers twice