I apologize for not answering requests for elaboration sooner, but it seems Draco did it pretty well anyway. The positioning is key. You have to do your best to position yourself so that when you disengage you fly over the middle of both rifts. It's not something I would rely on doing 100% of the time, but I do specifically look out for when two rifts are near each other.
Basically, just get as close as you can with your back to the first and lined up in such a way that disengage will take you over both rifts. When you land you'll have cleared both and gotten only one debuff. Disengage also already allows you to negate the damage closing the rifts cause so there's no penalty there.
For some reason my raid always seems to get two close to each other over by the tanks, so I either hope I'll get sucked into the far prison or I wait for some downtime to go over there. Glyph of disengage is certainly helpful here.