After this was posted I changed my DCT to 10W-30 HP4S. Prior fill was 10W-40 GN4.
Have 2500 miles on the HP4S. Shifting is smooth, marginally quieter than before. Temp gauge rises to 3 bars more quickly and is less prone to drop to 2 bars. (Has never risen to 4 bars or higher). In hot ambient (say, 80s F) or hot driving conditions (urban; twisties), the bike noticeably throws off more heat in the area of the clutch cover and DCT solenoids, but not uncomfortably so. Average MPG is better by 0.5 to 1.0; on the HP4S the bike has produced its best all-time full tankfuls twice (roughly 47.5 MPG).
I think the HP4S is a very fine cool weather oil — engine heat throw keeps rider warmer and may as well enjoy the superior MPG. If I were doing a lot of desert riding or going for a multi-week tour fully loaded or a lot of riding with pillion, I’d probably go back to the 10W-40 GN4 or some other suitable multi grade that ends in a 40 such as the Rotella and Maxima oils mentioned elsewhere in this thread.