It would be a sod in a strong cross wind.
Please, don't answer if you have nil experience in using a disc wheel.
To the OP. That German magazine that keeps doing all those cool tests but only release their literature in German have found a simple answer. When they were aero testing different TT frames and wheels they found that the biggest difference 'in equipment only' (remember the rider produces the largest amount of drag by a fair margin) is what wheels you use. There was little difference between the leading aero frames but the wheel choice made the biggest difference in numbers. So the short answer is yes. Definitely a yes for the rear wheel and even a disc on blowy days is easy to control. I've ridden a TT in 40km/hr crosswinds with 60km/hr gusts and I am very thankful I took my bonty xxx lights at the front, the disc was not a concern. So, since rear wheel has very little affect on handling of your steed the deeper dish you get the more aero benefit you will get. Double check though as somewhere along the grapevine I heard that UCI does not allow you to ride with as deep as the 1080 wheels but 808 is fine. Remember Highroad a couple years ago? They road with 808 rear and 404 front.
Your concern will be windy conditions and the front wheel.....always.
Keep in mind that when there are crosswinds there are several factors that will affect your control. The strength of the wind of course, how much weight you have over the front wheel as well as your weight, how deep are the rims, how many spokes are in the front wheel are the big ones. Another is weather you have bladed spokes, they can make a difference. Also your speed. When travelling at high speeds even a low spoked wheel will get a disc like effect.
Hope that helps.