It seems to be implied that we were higher up than I could descend in one round, which is only twenty feet. Also, there is no such thing as "wasting" Feather Fall for me - I can use it at will. My only limited spell-like ability is Dispel Magic, which I can use 1/day.
My thinking was that I could use Deeper Darkness this round, drop sixty or eighty feet or whatever it is to the ground (his spell has a maximum range of 85 ft, so we have to be reasonably close but not right on top of them), and Arduniel would be able to then see to act normally. At worst he should be able to just fly straight up out of my range as a move action and then cast using his standard action.