I'm probably not using archers right. Besides from the guy with wings which is indeed an awesome archer, the regular ones I can't get to deal much damage with them, even against mages.
I was kind of stoppiing using archers to use more mages, but since you say they're so good I'll give them another shot.
He's right. Get trueflight, strengthen and tremendous shot and make sure that you use archers on hills or roofs, if you can. The damage multiplies and magic happens.
My archer can almost one shot wizards now.
Don't forget trajectory, it's especially awesome when you try to shoot past your normal range, as it shows if it can make it.
My archers both use trajectory, anatomy, bows (obviously), strengthen, trueflight, counterattack, and fortify, plus a move I forget offhand. I also worked my butt off to get advanced weapons by doing a lot of grinding. 2 hand bows>>>>>1 hand bows when you're an archer, though on Canopus I stick with 1 handed for the use of a melee weapon (axes). I can kill most any non-heavy armor unit in 1-2 shots in story progression, and 2-3 in a training run (random battle).
One last suggestion for archers is to always stay a square or two out of your firings range. If you're above your opponents height level, odds are you can land a shot from further than the 3-7 square range you're shown. On the last battle of chapter 1, I can hit ANY TARGET on my first move using my archers by firing out of their given range.
As I said earlier...archers rape ass.