If you activate the Barbarians in Civilization, you are in for a world of trouble. You might want to just deactivate them and save yourself from ruin. The Barbs are really one of the weakest points in Civilization 5 and they aren't getting much attention or really being addressed very much at all - not neawr as much as they could be and should be. You really can't just go out with two scouts and expect to find Barbs and just blow them up anymore. That's just not happening. And one other thought is that raging Barbs aren't really raging if you are in a particular combate mode, you know.
So, I would say just deactivate them all together and save yourself the worry and the frustration unless you are really, really into them. And, if you are - practice is the only thing that is going to help you to figure it all out...practice, practice, and...more practice. That is the only way you will get better and really master the game and beat the Barbs.