I've used the D1's since their introduction, used them in both cold (British Columbia) and warm waters, and just recently the D2's. At first I did pan on the specs as I felt there were no benefits to upgrading. Then on a recent trip, I flooded one of my D2's, totally my fault, I was still jetlagged and didn't properly clean the 0-ring after silty muck dive and water entered the battery area. So, while I I was drying out the strobe in a bowl of uncooked rice, I put one of my D1's back in service. I immediately missed the quick recycle of the D2 even when not shooting full power. My buddies and I saw a blue ring octo and you could tell in my shots that the D1's were definitely slower than the D2 as the first couple-3 were evenly lit then the D1 started to lag a bit power wise while the D2 was obviously brighter. I'm still keeping the D1's as backup but my primary shooting will be the D2s.
I was able to successfully revive the D2 after cleaning the battery compartment with white vinegar, then a douse of rubbing alcohol then an overnight soak in dry uncooked rice.
Just returned from the Philippines and got to use the Sony A7rmk2 in the Aquatica A7rmk2 housing. For wide angle, I used the Sigma 15mm in EF Mount with the Metabones adapter and the Aquatica 4" minidome, I also got to use the Sony 28mm f2 with the fisheye conversion lens using the Aquatica 6" acrylic dome. Both worked extremely well with the camera and port combo.
I was shooting the A7rmk2 against my 5dsr and will have a review up on my site shortly
I thought I'd miss the 10-17 when I went FF, I even tried it with a 1.4 TC on my 5dmk3. Looking at the images, most were shot with the lens racked back to 12 (any wider and the dome appeared in the image), so now, I shoot the Sigma 15mm with my 5dsr. Next week, I'll be taking the Sony A7r2 with the 28mm with Fisheye adapter to the Philippines. I'll also have the Metabones adapter with the Sigma 15. You can't get wider than 180 degree diagonal without going to the Canon 8-15. Your other option is the Canon 11-24 but that's less wide than a 15 fish.