John--
I've not cooked ribs in the WSM with no waterpan. I've cooked them in a kettle that way though, indirect, numerous times, and have cooked them directly over lump or wood embers in different kinds of closed or open pits.
In a closed pit (or closed kettle) cooktemp is a product of the amount of lit and the amount of air intake/draft. Control these and one controls cooktemp: temps need not get sky high.
In an open pit one controls cooktemps (which means temps at the grate immediately under the meat) also by quantity of lit and by the distance the meat is placed above the coals. If the grate is fixed and distance is not variable, most cooks simply use frequent flipping and, quite often, a water-based baste to control cooktemps. This method is the one used most often by many ranchers I know in my area: open pit, wood or charcoal for fuel, direct cooking, frequent flipping and basting. (Basting with a water-based baste--in my area, often grapefruit juice--cools the meat's surface after flipping.)
A few Q joints around the country use this method as well. Cooktemps at the surface: 325-350.
I use the WSM when home because I can do other things while the ribs cook, and I use an empty foiled pan to minimize cleanup. I like ~275 for spares (though I've cooked higher, as shown above), and 325 for backs.