There's a bit of a maintenance routine when our boat is moored. Our latest 22 has a single pump under the motor bilge, and when it's clean it works very well. What happens though is debris, leaves, fishing line, etc. gets washed back into the bilge during rain events and when I'm washing down after returning to the dock. I find that the screen on the pump gets clogged and than the pump no longer works worth a darn. This requires me to get down and manually clean everything out every week or two while the boat sits at our dock. It's not a big deal, its just something I've gotten accustomed to doing.
We have taken a large wave over the transom in Saratoga passage in the Puget Sound on our previous 22. This boat had a single bilge pump in the step below the door. Spot shrimp season was closing within the hour, and a gale had unexpectedly picked up causing some of the roughest conditions I've ever boated in. Not wanting to be fined by fish and wildlife for having gear set outside of the legal window, we chose to brave it and retrieve the weighted pots. A big wave came over the transom resulting in 8-10 inches of water in the cockpit. It was frightening at the time to say the least, but the boat handled it fine, we still had plenty of freeboard left as the pump did its thing and baled the water out. I had turned the bow into the waves for safety as it pumped out. Not something I'd like to experience again but the boat proved itself relatively seaworthy. I don't think not having scuppers is really an issue, but keeping that bilge pump clean of debris, the wiring in good shape, and tested regularly is important. And I'll echo what was already said about bringing a bucket. We always have one, which has many uses, but can invaluable in case of emergency.