Jeeze, First of all, to help those ball links out a little, I would take a pair of piers and give them a squeeze while they are on the ball.......that helps to seat them against the ball, and can loosen them up a little.

You say that your swash is level, when everything is centered. What I always do when testing the electronics is to either un-plug the motor, or disconnect the speed controller and connect a battery pack to the same channel, in it's place. That way I can mess with the electronics, without worrying about the motor firing up. Try moving all of your sticks around, and observe what happens. You should be able to easily see if one servo is binding etc.

Also, do you have Expo, or dual rates set up on your controller? If dual rates are set, and the controller is in the lower rate mode, you could be only using a percentage of your full servo travel. If your Expo is on, and set to high, it could also give the effect you mentioned. Expo dumbs-down the stick sensitivity around the center point, but doesn't effect the stick at full travel. If your expo is set to high, you would feel like your sticks weren't doing much until they are at their futhest from center.