Here's a idea.
When the Kirin is dying, everyone in the party places bombs at the base of the climbable walls. Specifically at the wall underneath the wedge beetle that's one floor above where the Legianna lands, or at the base/top of the long climb before the high nest. The 2nd option is likely more viable, because the wedge beetles in the area will allow us to reach those spots faster than the Kirin.
Since it always takes that route when it's dying, it would be a good opportunity to intercept it at those points and possibly knock it down. Not only that, but it's a guarantee that it goes to sleep once it reaches the nest which will allow us to set bombs down anyway. So using bombs as it's running away will maximize resources and likely kill it faster.