There was a time when bouncing 3x your HP in a heavy tank was possible, but I have not bounced 1x my HP in last year, let alone 2x or 3x.
I even bought the 112 to get past this mission and I have had games where I bounce ZERO shots or maybe 1 snap shot.
Relying on your armour in this game is actually impossible, unless you are in a cheiftan or 279(e) or some other russian supertank. And even then you will just lose HP to cupola sniping or the shot misses your tank entirely. Most heavy tanks are just HP to get farmed, they are slow, have terrible guns and don't actually have armour. I will never understand Wargamings idea behind this mission, it is a mission entirely without skill, the only way I have ever seen someone complete this mission is against an entire team of idiots spamming shot after shot of regular ammo… And that just doesn't happen anymore.
There is such a thing as a "penetration indicator" that every single player uses, so why would anyone take a shot at a tank when the indicator says they won't penetrate? So they don't fire, then they ether wait all game while your entire team gets killed first, you push them and expose your weak armour, or they load gold and auto-pen your superstructer and cupolas.
Source: https://www.reddit.com/r/WorldofTanks/comments/ulfggu/ht12_is_actually_impossible_now/