I do feel for Martin and the others who had problems on this trip, but I'm still very happy and confident in my 5DmkII (which was on the same trip). I had no problems.
FWIW, when off the boat I carried my gear in a SlingShot 300AW. I had a 40D and a 5DmkII, and on shore most of the time one had a 100-400mm lens, the other had a 24-105mm. I also had a 17-40mm that got used on shore a couple of times. The bodies were stowed in the bag with the lenses attached. I did change lenses on shore a couple of times.
On the early landings we had with lots of rain, I was using a single body at a time, with a simple Optech Rainsleeve bag over it. I did use the cameras uncovered in the rain a couple of times, but only for light rain and wiped the rain off soon or put the bag on (drying the camera first of course). Some landings I left the SlingShot on the beach, but not when there was rain. When traversing the ocean in a zodiac, the SlingShot was on its side in a Seal Line WideMouth Duffle between my feet (a waterproof bag which should even float if it goes overboard). This arrangement allowed me to open the duffle, reach in, open the side of the SlingShot and extract/insert a camera with lens if I was shooting from the zodiac. I did also have a G9 with UW housing which I used over the side of the zodiacs and for general shooting where water might have been an issue. I'm sure I missed some opportunities when my SLRs were buried away (and I'll probably operate slightly differently next time ) but overall I'm happy with the result.
I usually also had a small towel inside the duffle. When on shore the duffle was left with the lifejackets/etc above the beach. On the early landings where it was steadily raining I used the AW cover over the SlingShot on my back. The bag did still get damp from the rain running down my back (outside my jacket). When a camera went into the SlingShot the Rainsleeve was removed. There was always some moisture inside the sleeve from condensation, even when out in the cold wind for ages.
I was generally impressed by the Kata raincovers, thinking I should have taken one. I don't know if some people left their raincovers on all the way back onto the ship and into their cabins without drying off the internal moisture? Lots of similar operational issues were surely factors, as well as any construction issues.
I don't think I "mollycoddled" my cameras, and I think they performed very well. But then for years I've been using EOS bodies (D30, 10D, 20D, 350D, 30D, 40D) in environments such as the Serengeti, outback Australia, pelagic birding trips (small fishing boats on the open ocean), tropical jungles and mountains in Borneo/Laos, etc and have never had a body failure (apart from a loose connector inside the D30, BG-E2 failures on the 20D [but that was a P.O.S.], an issue with dust around the hotshoe of the 20D blocking use of the internal flash, and one time I dropped the 30D). Dust, snow, rain, humidity, dew (think star trails), etc. Maybe it's because I'm lucky. But the 5DmkII didn't disappoint.
Maybe a manufacturing issue with a batch of cameras was a factor. Mine has a reasonably different serial number than the failures identified so far.