I've used endura road overshoes for a while. They keep your feet insulated even when water has eventually seeped in. In heavy rain they keep feet dry for about 45 minutes (without mudguards). This does require taping up the vents in the shoes soles with gaffer tape. I presume water gets wicked from below round the shoe but mainly comes down the tights or socks from above.
They are fairly fragile though, neoprene is easily nicked by sharp chain rings etc. Also I've repaired the left toe where I normally touch down more than once, but it does get a lo of wear. My current pair have also been holed extensively by a sliding crash, and need replacing.
The one real design fault in my opinion is the strap at the top doesn't have normal velcro hooks but some type of plastic pillars with a mushroom top, that just doesn't grip the loop fuzz properly, so I often find I'm having to push it back on, and this gets frustrating. It was proper velcro on the first pair I had.
To replace the endura's I thought I'd try a similar version from another brand, so got the BBB Hardwear BWS04, but when the 43-44 sized pair arrived they were too big for my size 44 shoes, baggy at the front and not a snug tight fit like the large endura's had been. I'm currently waiting for an exchange for the next size down. They seem to be basically the same, slightly bigger openings at the bottom, but still within he hard sole, but PROPER VELCRO! so hopefully they'll be as warm and waterproof.
That is pretty much all my overshoe knowledge from personal experience.