No, the serenity capstone is pretty well balanced. It's very powerful, but it's powerful for an ability that usually only pure monks will care about. I actually like serenity.
And I don't really know what your point is? That some people didn't want to multi their paladin, and they expected some sort of bonus to do so? I always thought those people were silly. 3.5 is based around multi-classing.. that's why there are so few classes with a lot of upper tier abilities.