The Caernarvon heavy tank should never have been artificially uptiered to 7.7. It completely fails the triad of Firepower / Protection / Mobility.
It is not a fast tank, basically on-par with normal 21-22mph Centurions. Its not sluggish, but it’s nowhere near close enough to justify facing ever-faster vehicles at the higher BRs.
Its gun has immense flat-armour pen but it has no real zoom on its optics and thus cannot fight at range and because it is 7.7 it almost purely faces angled armour that it has little to no impact against (there are many 7.7 Medium tanks that are, for all intents and purposes, immune to anything but the most pristine critical shots from the Caernarvon because of angled front armour and rounded turrets, as it can barely take on 100mm at 60 degrees). To top this off, British APDS is immensely prone to being absorbed by the first thing it hits, meaning that it typically cannot disable enemy tanks ability to shoot back, and rarely KOs them unless it precisely hits the ammo (and nothing else before it). You are fully dependent on side-shots and even then there is some luck to not have it do nothing.
Its armour is effectively non-existent. Face-to-face with a Tiger II (supposedly a same-role tank that is 1.0BR weaker than it), the Tiger II almost cannot fail to one-shot the Caernarvon no matter where it hits; it is fundamentally difficult to not KO the Caernarvon save for some awkwardness on the turret, but if the hull is even 1% exposed then you can go straight through the Caernarvon’s entire crew almost regardless of what tank you play. Contrast this to facing the Tiger II, the Caernarvon has to precisely aim for the turret cheeks whilst the Tiger II just has to roughly connect a shot, at which point the Caernarvon must still hope its weak APDS isn’t absorbed and reaches the ammo. The Tiger II is almost immune to being one-shot KO’d by its supposed full-uptier rival, but the Caernarvon has nothing to defend against it, no matter the distance, perhaps even worse with distance as the requirement for pinpoint accuracy on British guns is let down by Gaijin’s magical “cold war started and now nobody has gun sights that see anything” optics.
Against full uptiers at 8.7, the Caernarvon has nothing. If it isn’t a lightly armoured IFV or light tank, it won’t do much, and even then it frequently can’t disable them and so they just lob a missile back and that’s you done-for.
In summary, the firepower is extremely situational and has been nullified by its raised BR, its armour is so weak it’s almost a joke to call it a medium tank never mind a heavy tank, and its speed cannot balance out those deficits. It is fundamentally a big wide target that can’t take a beating and is no longer allowed to dish one back out. Its only redeeming feature is the stabilizer.
To that end I think it should be at 7.0, where every 6.0 and 6.3 in the game will still be one-shot KO’ing it with that terrible armour, but at least it might fight back.