wedge is useless as it is...

but I do use a wedge formation with a pure caval army of at least 9 units
1 front center 3 behind 5 last row, forming a wedge while in square formation.

Effect on impact:
1. unit hits and gets stuck in melee , 2. row hit same thing, 3rd row hit ...the unit/units engaged by 1. row tends to break when the 3rd row hit.

It work very well with gothic caval or legionary, I would not do this with light cavalry tho.

Final effect is: broken center of enemy army- exposed general in rear- dead general unit- 50% of enemy runs befor you loose 20% of your troops.

P.S. dont ever try that on phalanx-formations.................