I have to say that this set is very overrated.
Ok it had two Crusaders, which is nice. However a lot of sets in the classic era were just as good army builders. Spears are the worst weapons as they are so easy to obtain.
But back in 1986 weapons were more evenly distributed. You were just as likely to get a bow as an axe, a sword, a lance, or a spear. Spears as ballista bolts (back then or today) are realistic. They are probably too dangerous today which is why the new ballista set does not use these pointed objects

Other than the spears it has a bow, which is nice, but I feel that Battle at the Pass is a much better weapon builder, and it's a modern set (it is only relatively around 5 times more expensive than this set and has a much greater variety of weapons and a LOT of weapons).
Battle at the Pass is a mid range price set which probably has the highest weapon to minifig ratio of any castle set. Comparing 6012 to 8813 does not make sense as they are completely different sizes. 6012 should be compared to Vladek Encounter or Viking Warrior Challenges the Fenris Wolf which have similar sizes and piece counts.
There is also no shield which places it behind a lot of other army builder sets from this era.
There is a shield on the front of the set
If this were released today with say Shadow Knights, bley and new-brown, I wonder how many people would rate this so highly.
The set only has 5 grey pieces and is mostly black.
I can't give this set more than a 3/10, and only that high because it has a low price point for two desirable figs.
I agree that better ballistas could be developed with today's elements. Nathan Well's Ballista is an excellent example:
http://www.mocpages.com/moc.php/4839
The true advantage of this older set compared to modern sets is the excellent brick and plate selection. You can actually build other things out of this set. Check out the inventory here:
http://www.peeron.com/cgi-bin/invcgis/i ... thpics=yes
Ben