I use the wedge a lot. In the Acre battle AAR I did, Saladin's unit can be seen using it. If you have one or more really strong units, you can use the wedge to rapidly smash your opponent's units one after the other. It doesn't give you better odds, so if your unit can't beat another unit, the wedge won't change that. However, if your unit can beat another unit, then you do cause more damage more quickly with a wedge, so that your target either routs or is destroyed in a hurry.