One key advantage of this card in a mixed fire/darkness or rainbow deck over steal is that it is only 2 quanta.
If youre faced with an early discord played against you, 2 quanta is a lot more doable than 4 quanta for a steal.
Thus even if steal is normally the better card, as it gives you card advantage, in this situation defrag shines.
Also, i usually include 2 in a 32 card grabix style rush deck, as enemy shields are the major reason this type of
deck loses at all. In this instance i usually save them for the more obnoxious shields such as fireshield/ dimensional shield/ dusk shield.