Hi Jennifer:
I haven't personally tried the Doc's Proplugs, but I have looked at them. The version of the plugs that are sold for diving are "vented" meaning that they have a hole in the middle allowing water to enter your ear canal so you can equalize.
The best theory that I've heard on how they might help you equalize is because they slow the pressure changes when you descend. Not sure if that makes a lot of sense. They might have an important placebo effect, but that's just speculation on my part. I wouldn't think that having the plugs fall out at depth and causing barotrauma from rapid pressure changes would be a big problem. They are vented, and seems like they would be unlikely to fall out on descent because if there is a pressure gradient it will be pushing them into the ear, and the pressure gradient on ascent when the ear canal is already full of water won't be great enough to make a difference. You could try them and see if they help you equalize. If they do, great.
The idea that they would reduce the risk of ear infections by keeping dirty water out of your ear canals seems suspect to me. The diving plugs are vented, so they don't keep the water out. Hmmm....
The claim that the plugs might reduce ear canal problems by keeping out cold water makes the most sense to me. Cold water can stimulate the growth of boney growths in the ear canal called exostoses. These growths can narrow the ear canal leading to problems. Seems like the plugs might reduce the amount of water that is exchanged in the ear canal during the dive giving your body time to warm the water (kinda like a wetsuit). They might make some sense for cold water divers. (But if you're already wearing a hood in cold water, I don't know just how much water is being exchanged during the dive and how much difference the plugs would make?)
HTH,
Bill