Getting a patio table at R & C really is pure "luck of the draw", so to speak. They no longer allow you to request a patio table and wait for it to open. You are required to accept the first table that becomes available for your party size.
We have eaten on the patio 3 times, and while it was really nice and we enjoyed it, there are better views of Illuminations from different spots on the lagoon. We were on the upper patio and the view was parially blocked of the higher fireworks.
I think 8:15 is late to expect a patio table to open. Anyone there at that time will most likely be staying to see Illuminations. I would try checking in earlier and requesting a patio table, but they may ask you to come back 15 minutes before your ADR and then I don't think your chances are very good.
Good Luck