Everybody has their own system. A lot depends on where I'm going. For Palau and the soon to be Lembeh trip, it is all packed in normal roller carry-on bag that does not exceed the 45" limit. This is the multi-leg, multi-carrier, by God I may not have any dive gear but I can still take pictures, carry it all with me approach.
I have a pathetically old and crappy one at that. This bag has no excess padding (i.e. light) and no useless outside pocket. One thin layer of foam from the Peliccan 1550 or whatever it was on the bottom. Everything goes in, including ports, cables, two strobes (one backup in checked bag, rolled up in wetsuit inside SO's jacket BC). Tupperware for parts. Underwear for more padding and 20 year down pillow (hardly anything left to old "woogie" on top for more padding.
Now, since we travel as a pair, the camera gear goes in a Lowepro AW Trekker along with all sorts of stuff. I could have put camera and two lenses in the bag if I had to. If I were a solo traveler, I'd get a bigger backpack laptop bag.
When I carry for land photographry, too, a lot of stuff gets checked. Too much to carry. Tripod, long lens, polarizers, filters, flash, TC's, etc.
If you are fighting for room, check the dome port and one strobe. I pack the dome in the box in which it came, stuffed with socks. If the checked bag doesn't make it, I can still shoot macro with one strobe.
I have a shooter's vest. You can wear one and stuff all your lenses, filters, cable in the many pockets. Mine has a pocket at the bottom back of the vest that can handle a 300mm lens. They will look at you funny and your back will hurt after a while. Just another option.
I think my SO would prefer I use an MX5 and a Minox for land use. She once toted a 30lb. backpack for me. But the trail wasn't really that steep, just muddy and wet. 