I'd have to correct you on that one. Ship cannons could actually be aimed individually. It was a bit unwieldy and also not always neccesary because even though cannons had much longer range, between 1000 to 2000 yards or meters, the accuracy at that range was laughable due to the unpredicable trajectory of round shot. The effective range was a couple of hundred meters.
Carronades were actually relatively easy to aim individually. They were often mounted on a fixed undercarrige made to turn left, right, up and down with ease. The range of these smaller cannons was a bit less though. However, naval battles were often fought at around 100 meters from the enemy, so range and accuracy wasn't a real issue. Carronades were accurate enough at that range. You just had to put as much shotweight as possible towards the enemy ship. You'd allways hit something at that range.
By aiming your cannons you could fire your broadsides without being directly opposite and parallel to your opponent.
Just out of interest, since I wasn't present during the event, I'm curious on how a ballista would sink a ship?
At what range was this fight taking place?
What kind of ballista was used?
A bucket of water would be enough to put out any fire caused by aflaming ballista arrow, unless it somehow landed right in some gunpowder, which is highly unlikely since ship crews were VERY cautious with gunpowder. Powdermonkey's (young orphans) ferried gunpowder from the powder magazine deep in the ship's hold to the artillery pieces, often as premade cartridges, to minimize the risk of fires and explosions. No gunpowder was stored anywhere near the cannons. I imagine volley after volley of fire arrows would be more effective to eventually set a ship on fire, but the range of those arrows would be far less than the range of either the ballista or cannons.
Ballista's were mainly anti-personell weapons. Quite terrifying and pretty accurate ones too as they could easily kill multiple soldiers, with armor, in one shot. Very effective when wars were fought with huge solid formations of soldiers. Most ballista's were not bigger than a 6-pounder cannon, with some (huge) exceptions shooting up to 3 talent (70-80kg!) projectiles. Still, a 80 kg, low speed projectile would not do anything against a 40-60 cm /15-23 inch wooden hull. The newer, better built hulls could -bounce off- up to 18-pound rounds from close range (that was in the 1800's though, sou outside of the time-scope of HW). The huge ballistae would have needed a crew probably bigger than a gun crew, would not have been able to aim at a moving ship and the rate of fire would have been the same or probably even less than a cannon.
Considering the short distance between Breakwater and the WE remnants of ships I see on the map, it would have taken some really bad marksmanship on both sides to even miss a single shot fired...
Now, a ballista shooting burning barrels or balls of tar or oil... That would strike fear into any captain...
I understand the fact that the cannons might have been nerfed because of the wide array of medieval time periods people play in, but in fact, ballistae were at their best during the Roman empire. The knowledge to build ballistae that good was like many Roman technologies lost in the dark ages.