Thanks for sharing your experience. You ask if Gate Pose can be good for Yin Yoga students: sure! No, never! Maybe, sometimes.
As always, it always depends. Gate pose does require some muscular engagement to stay in the posture; the side body is working and there is a need for balance. But, so what? Camel Pose and Swan require some muscular engagement and they are used in Yin Yoga. I would just suggest you not hold any of these postures too long. Maybe 2 minutes maximum? It depends upon your students. For some, even 1 minute may be more than enough.
The question I would ask of any teachers is - why? Why would you put someone in the gate? What areas are you targeting? And, then, is this the best way to target that area? When I do the gate pose, admittedly only in a Yang class, I am targeting the side body --- trying to get a nice stretch there. In a Yin mode, I can do the same thing but for longer if I use Bananasana
. Have you tried that with your students? You might find it works the same area, but in a more yin way and you can stay longer.
But, still - I am not saying Gate Pose won't work for your students. You have been teaching it already, so - what results have you found? Does it work for them or not? Maybe only for some?
Why don't the students like Sleeping Swan? Is it the knees? Maybe they would do better with the sitting or reclining versions.