For real, that really bugged me when someone posted a video showing how "OP" the kannon was. That loota was alone for most of the video, and NO ONE ever tried to go kill him with a Jump Assault? A kannon user is even more of a sitting duck than other heavy weapons, since the "snapshot" is totally useless.
EH I used it mostly cause I don't play CSM As for non LSM well how about those Striking Scorpions for the Eldar which can turn invisible literally two hits to the back from one kills an Ork. For CSM you guys do have Abbadons Disgrace though like I said I don't play CSM to often. Biggest thing to remember for the Kannon is this you can see us clearly we are easily the biggest Orky Targets due to the tank gun we have perched on our shoulders.
If anything, what the weapon really needs is a trail. Leave a smoking trail behind so everyone can see where that giant, supersonic explosion came from and I'll call it a day.
The lob grenades only deals damage to infantry and is not a 1 hit kill. When charging a shot the rate of fire is slow as hell compared to other heavy class weapons.
Short information about the Kannon as it seems lots don't know it: It can onehitkill every loadout as it deals 1600 dmg with a charged shot. 2S charging timer (got reduced, prev 2.5s). 2S reloadtime, 1 shell/clip. It can onehit very soft targets with the uncharged shot (basicly a high velocity grenade) which deals 300 dmg at 80 pen which is insanely hard to aim as it is a timed detonation. (i don't know any non-okr weapon even coming close to this in terms of managing to hit) It costs 500 LP, mastercrafted costs 580 and is currently worthless. It is best useable at 50+m. range upwards only limited in aiming and seeing skill as it has no scope (even though it has one built on the kannon itself which does nothing else than covering your sights) It is only limited usefull below 30m, in terms of guaranteed win against enemies who don't see you and a fair chance against enemies if both surprised each other and the enemy has a short range weapon (as the stormbolter). A prepared enemy with a halfway rangecapable weapon will kill you. It is nearly useless below 20m. If you manage to ambush your enemy or have full height cover (and the enemy no cover at all). If both are surprised (not aware of each until this moment) you have barly any chance at all. Short from. it will kill you with ease if distances are 50+m and you should kill it with ease if its <20m. And if you get ambushed you would have lost to almost any other heavy weapon. If you don't manage to to kill an loota at 10-20m who didn't ambush you, then you deserve to die to this loota.
The rest of your post was just dribble but these bits are the real gems. You consider adding a cosmetic only change a straight up nerf? Hugely overblown and hyperbolic overgeneralisation. And to the second part...lol. I can't even one shot an Ork in the head, let alone their back. Obviously you want to keep riding the gravy train and you'll say just about anything to keep it that way. Biased Ork response.