Also, he's not exactly saving them, since they are (a) surviving well enough on their own, even if their universe is not as radical as it once was and (b) not necessarily happy to be summoned to Doc's reality, as shown by Ron's reaction to the news about bad pizza.
Edit: When was it stated that people from the radical lands are dying? Sparklelord has already been banished, and all I remember are vague allusions to his corruption spreading and the radical lands becoming less radical, not that people are dying in droves or anything like that.
My prediction (insofar as the plot of Dr. McNinja can be predicted):
SpoilerChuck Goodrich will show up and foil King Radical's plans, possibly in some sort of massive anticlimax. Not "our" Chuck Goodrich, but another one from the future of another reality where King Radical has succeeded. After all, "Every parallel universe has some global tragedy, and Chuck Goodrich will always be the man to find a time portal and try to prevent it." And Radical himself seems to expect that a Goodrich will try to stop him at some point.