I tried this blocking thing last night, and it worked like magic! The Venetians were attacking a bridge held by my about even forces. I placed to Catapults right in front of the bridge exit on my side, with XBows to the sides. The enemy charged across the bridge and took a few hits of flaming catapult goodness, but then they had to stop, blocked by the Catapult's mass. Only time and again most of a unit would manage to extricate itself from the crowded mess their army had become, to be stopped cold by my pikes. Ouch. Five units of Crossbows rained death into the middle of the bunched up Venetians. After my arrows had run out, I just charged in everybody and simply wiped them out. A bit cheap, I won't be using it much for this reason, but a great find!