Bass seemed to survive as I was on the pond for an hour or two after catching them.
If you can see to the pond's bottom, there's a good chance you're correct. If you can't see to the bottom, you have no way of knowing what happened to those fish, because dead fish don't immediately float to the surface. They almost always sink; in my experience, they always sink. A fish doesn't float to the surface until it begins to decompose. Decomposition generates carbon dioxide, which makes the fish buoyant.
If you intend to kill a fish, i.e. it is headed for the frying pan, then fighting it to exhaustion is not an issue. It's another matter with fish you intend to release. Those fish should be played quickly, maximizing the chances for survival.
It might be that you're among those experts who know how to subdue large fish quickly with even the lightest tackle. We average folk should match the gear to our targets, just as you would when hunting.
The Federation of Fly Fishers was a pioneer in catch-and-release fishing. You might want to check out the information posted here: http://fedflyfishers.org/Conservation/Policies/CatchRelease.aspx