Short version: buff the damage cannons deal to players
Now that "too long didn't read" people got the point, lets get to explaining :P
In my opinion the damage cannons deal to players simply makes no sense and has no reason to be that weak. I am saying this because I saw what happened at recent siege. So here is a little "story time"
around 6-7 "opps" were capping the banner on a siege chunk and tanking shots from 3 cannons at same time directly, for more than 7 mins and nobody even came close to dying. I spent around 130 shells and it all went straight into crowd and I was not alone in shooting at them, and they still managed to cap it anyway. And that is not even the biggest part of the problem, I would understand the argument "but Nuxyr, it would be unbalanced if you could just sit on cannons and camp the siege chunk and then nobody can do anything about it". But what happened next is, after capping the banner, the opps just showed up with 2 heavy tanks anyway and completely wrecked the cannons and disabled them. It just goes to show that they were perfectly capable of dealing with cannons but they just choose not to, because why would they? its not a threat, and if it ever becomes, they can just cry about it and then it gets nerfed into the ground.
In my opinion, it would be perfectly reasonable if direct hit from a cannon can straight out kill a person, as it used to be for a very very long time on CCnet even before heavy tanks were a thing. If the "opps" were capable of just rolling in with heavy tanks, and then destroying the cannons and capping the banner AFTER they dealt with the cannons while protected by tanks, THEN I would consider that a fair fight and a balanced gameplay. There was a treat, they had to overcome and neutralize before going for the win condition. As it is right now it makes no sense to even bother with cannons, because they only threaten tanks and tanks in turn only threaten cannons, and Infantry can just decide they don't want anything to do with it and just cap regardless of everything else.
*Warning, triggered Nuxyr ahead*
And for love of god IF for the "nth" time Zaify buffs cannons a little, and then people just end up ignoring them and dying for it then PLEASE understand that its not a balance issue if you can not just IGNORE cannons shooting at you because you CHOOSE not to deal with them first even if you have a perfectly reasonable way of doing so >:( Like what is the problem? even if we had cannons dealing damage, they would literally just roll in with the tanks and deal with them and the assault would have been much more fun with both sides having win conditions instead of "oh they brought more PvPers lets just not leave fort and then do whatever we can from there even if it is useless" I know I had many "rants" like this in the past, but look how much the game has changed now. Remember the main argument against buffing cannons was the fact that people used like 40 of them at the same time completely obliterating everything with canister shots if they have the setup, while the same canister shots were completely useless when used in a single cannon. Now there are no more such contraptions and there is no reason for any ammunition including cannisters to be useless against players.