So, you're getting nine power and toughness (spread across three bodies) with trample for six mana
There were no good answers to a Frenetic Efreet, only answers that worked half the time, so as long as you weren't far enough behind that he was ignorable the Efreet was always effective
It is nice to have the slight flexibility with the plot ability though
I wish Gobbling Ooze started off as a 1/1 and cost something like 3 mana, because I like the other parts of this creature well enough
Check these out: Abzan, Bant, Esper, Jeskai, Jund, Mardu, Naya Sultai, Temur
Cards like Force of Will, Fierce Guardianship, Pact of Negation, and Force of Negation let you stop game-winning plays while tapped out, which is perfect for protecting your own combo turn or stopping someone else's