If you feel the slingers are too weak try tightening up their formation in the EDU, this makes them a LOT more powerful, as i recall the EB team losened their formation a while ago as many people felt that they were overpowered.

As for the cavalry i feel EB is spot on, a frontal charge into braced spearmen will be ineffective while charging swordmen will cause more causalties while charges to rear and flanks will result in a massacare.