Gargoyles make effective scouts and can be deadly if left to rain attacks from the air, but they have a very obvious weakness. Most of them have to go through long periods resting as stone to maintain the energy they need to carry their heavy bodies through the air.
As I peered through the eye you were using, I noticed dozens of iceskin sentries resting on the eastern and southern walls inside. Use the stalker to leap up to their ledges and devastate them while they sleep.
Almost too easy.
Not so much of a threat when they're sleeping.
More often than not the heave will destroy the gargoyle. Occasionally they'll wake up and just hover there.