Well I often find myself on the attack with the Irish. The tactic I have tried thus far is 3 Armoured Spear in the center with at least 2 armor and 1-2 valour. I then put 3 Bonnachts behind the spear. The armoured spear with their +2 armor are used to soak up the arrows, which they do fairly well. I then put 2 Gallowglasses with valour on each flank plus Mounted nobles and horsemen on the flanks. My spearmen are used to hold the enemy Huscarles (There is ALWAYS huscarles!) while my bonnachts throw javs. Problem is, once a unit gets to close to the bonnachts, only a few of them throw and even if they do all throw they got right over the enemy heads and land behind them. So they do absolutly NO good. The only way they would be useful is if I stoppped my Spear line some feet in front of the Huscarles, so their was space between the two, then the Bonnachts could wreak havoc. But come now, who is dumb enough to just stand their with their Huscarles. They are already charging me! So my Bonnachts do no good :(
The Huscarles just cut right through the spearmen and Bonnachts. :( The gallow glasses can never get into the fray fast enough because of all the cavalry entanglements on the flanks.

This seems to be the case from what I've seen... It takes the Irish at least 2 units to match 1 unit of Huscarles. And even then both units are badly depleted once they've won. Problem is, there is only 16 unit slots for both armies. Which means the enemy always matches me in numbers, except his are huscarles :(!