In Limited Cavern Harpy was a deadly card for the right decks, impossible to kill and giving you a lot of tricks to pull off
The competition for every free deck slot in Modern is intense, but nevertheless this card is still awesome
White also doesnt tend to get much in the way of mana acceleration, so this is a nice bonus for decks to try
In other words, it is possible to attack a party with all three physical attacks or a magical attack -oriented party
With Yuriko, the Tiger's Shadow , your whole deal is striking with low-cost, evasive creatures, then launching your commander into play with ninjitsu, and reaping the rewards: plenty of card draw, and plenty of pain
If they choose the latter then everyone is progressively weaker and youre better off for it