I remember playing an archer in a party of 3 (with Anomen and Imoen IIRC) a while ago. She ended up getting the vast majority of kills, thanks to grand mastery and the Tuigan bow.
Advantages over a melee fighter:
- 5 attacks per round, every round, as long as there are enemies left on the battle field. Extra fun with improved haste for 10/round! I remember thinking of her as my machine gunner in those days...
- killer THAC0
- can disrupt several mages per round (just pause and choose new target after each shot)
- doesn't get hurt, doesn't usually have to drink potions
- one less character that needs good AC, can use items that focus on other things instead
- can sneak (nice for scouting ahead)
- it's much easier to select the right type of arrow than to switch to the right weapon for the situation (e.g. switch between non-magical arrows, plain magical, acid arrows for stoneskins, arrows of dispelling)
It's been a while and I don't remember my tactics clearly, but I do remember it was one of my two most memorable runs. Actually, every now and then I think I'll have to do another one like that...
Crenshinibon, how do you get 4 attacks on a dual-wielding blade? He doesn't get any extra attacks from level-ups, so that would be just 2 for two weapons. Are you using both Belm and Kundane together or is there some spell involved?
Using Haer'Dalis, I found out recently that if you dual-wield (2 attacks, no Belm/Kundane involved), cast haste (+1 attack) and then activate offensive spin (another +1) you actually end up with 5 attacks rather than 4! I didn't have improved haste at that point, it might be interesting if it can be cast on top of that, too, for 10 attacks per round. All of these spells have a decent duration, too.
This combination should be valid for bows as well, as these also have 2 attacks per round regularly. Needs 3 spells rather than just one for the archer, but on the other hand, he'll get max damage out of it as well (from the spin).
Blades, just like the archer, suffer from a lack of AC because their items will probably focus on spellcasting rather than AC and they can't wear heavier than chain anyway. Staying back from melee and gunning arrows at 5/round with max damage each sounds like an interesting option to me. You can also use them perfectly well with a cast and attack tactic, getting a spell off every round, if that's not too cheesy for you.
The main disadvantage I can see with the blade is the lack of THAC0. The archer probably has the best you'll ever see on any character, while the blade is essentially like a thief. No problem when fighting mages, which should be priority for archers, but against clerics or fighters with good AC he might have some more difficulties.
The other classes mentioned pale in comparison I think. A kensai doesn't offer any substantial ranged bonus. An assassin has the poison, but only two attacks per round and, unlike the blade, no potential for self-buffing.