Archer is not OP - there are definitely weaknesses, but he is strong and almost as easy as a Warrior to play (if not as easy), so it's a good choice.

I just managed to win a battle vs six minotaurs, in similar circumstances to the above, with a warrior. Admittedly I've progressed far enough through the campaign to unlock second tier units, and third tier shops (very useful to have strong armour). What allowed me to win, though, was discovering that I could buy gargoyles from a sorcery school (and if I'd not already bought other second tiers I'd have loaded up my second+tiers solely with gargoyles). They were able to take two hits rather than 1, and even took down one of the minotaurs. The really important success, though, was when I'd been surrounded with minotaurs and beserked: one round attack killed 4 of them!

In future situations of that sort, remember that if you have/train up multiple heroes, you can attack with both in one turn. Even if the first isn't strong enough to win, the guards take some time to recover, which will massively increase your other hero's chances.

Yes i meant crossbows.. It seems crossbows are best weapon for archers(all types). Can yout ell me when bow is better in mid-end game?

Also...
1. What the hell is demesne? There are some buildings and i just dont understand the difference between demesne and province. And do all buildings really work as they tell?

If you have a pure archer (Sniper) he gets Precise Shot 7 when he gets high enough level, which means he ignores 7 ranged defense, making the armorpiercing property of crossbows redundant/ almost useless. So once you have high enough Precise Shot bows are usually better for range and Ranged Attack being better (unless you found a great crossbow and NO good bows...)

Demesne is your capital province with your main castle. Not any other province - just your capital. Province is any province that meets the criteria named (ie having a pub, or whatever). And yes all buildings do what they tell.

Yep demesne is a word I bet most of us heard for the first time, but it is an actual english word,I was suprised,too.

Demesne is a really funny word. It comes from french and rhymes with queen.

Yes, in the game it's just your home castle province.

Crossbows can be a good choice at very early levels when enemy ranged defense still means something, but quickly becomes obsolete once your damage and level of precise shot increases. Armor Piercing from crossbows halves ranged defense, but precise shot completely negates a given number of points of ranged defense (at higher levels the number of points in negates is more than most enemies have). The decreased range of the crossbow also becomes more annoying once you get over level 10, since with double-shot you can't use it if you first move (in order to bring your target within range). Much better to get a good range 6 bow which with the archer's increased range from skills basically lets you strike any enemy on the battlefield.

There's also a bow that gives magic shot, which makes enemies defend using their resistance value. I'm not sure how that interacts with precise shot though.