Despite proposing a possibly unstable trio deck concept, Chapuz has hit the nail on the head. This is a deterrent, a passive counter (an active counter to creatures would be something that removes creatures from the field, or deals equal damage back while ignoring shields). It is worthless against creatureless decks, and weak against stalls - in fact, the immaterial nature of the creatures it generates is a two-edged sword, since it's providing creatures you can't do anything but attack with. They can't be mutated, duplicated, momentum'd, blessed, whatever.
What I'd like to see if this were introduced ingame is an off-element card that plays a creature of some kind on your opponent's side of the field. It would take a while to set up, and wouldn't be an impossible offense to block, but it would rival Growth/Ablaze in terms of creeping power.