Not sure I'd say it was overpowered. Powerful, sure, and as Zen noted, under-rated.
But look at ... The gate stone, the flying ship, the Ark, the Chalice, the Hammer of the Forge Lord : I'd argue that both of those are more powerful in terms of altering game play and situations. For instance : 200 devils and other top-notch summonings teleporting on top of your armies at whim, leaving before there can be much retribution - I'd say that has a lot more impact than a bunches of scrawny wolves.