Having just tried shield wall in a siege defense for the first time (yeah, I'm a little late to the party!), I might need to ban it. It seems... unfair.

Situation: as Koinon Hellenon, I got Massalia by rebellion from the Romans, complete with a couple of units of Celtic Lesser Kings. I've never played with these before, and come the first Roman siege I'm wondering what to do with them. Their formation looks too loose for my standard street defense tactic, which is to put a beefy unit on guard mode in front, with some spearmen behind (so that if enemy cavalry pushes my beefy unit back into the spearmen, the spearmen get all stabby-stabby with their spears). I figure what the heck, I'll put one unit of Lesser Kings up front in this shield wall thing and see what happens.

A 3/4 Roman stack approaches the walls, thinned down by slingers and towers to maybe a half-stack by the time it reaches my main street - basically a full Roman legion. At this point I'm expecting my Lesser Kings to be pushed slowly back into my waiting levy hoplites. But no! The Lesser Kings proceed to push UP the street in shield wall formation, forcing the Roman horde back with every step. By the time the mass has been pushed back to the end of the street, it's exhausted and shaken, but starting to seep in around the edges of the shield wall. So I charge in with one unit of hoplites, tell the Lesser Kings to go to town (off shield wall, off guard mode, attack) - and they rout the lot.

Shield wall turned the battle from the usual tense "will they push me back far enough to disrupt my formations and end up as a slogging match" to something of a joke. I mean, two infantry units routed a legion. Seems unfair to the AI