How is the hp pool “barely adequate”? It has over 1000 health. If you let it eat four to five volleys (assuming you get suprememly unlucky with rng from atgs or TDs then you’ve messed up.
Most tanks also can’t take that much damage.
It's incredibly common for it to take multiple volleys. Especially if you want to let it fire a shot in retaliation. The alternative would be for the KT to poke out, get hit, retreat without firing because of its turret traverse, and then you don't risk losing the KT but it's just going to be 26pop of upkeep that does nothing the whole game.
If players were to use the KT as hyper-conservatively as you suggest (never being in situations where it could possibly be endangered) then it would be an expensive and worthless piece of garbage that eats up 26 popcap.
It sounds as if you've never used a King Tiger before. The KT's acceleration value is so bad that if you're slightly slow to retreat or stay to get a shot off, you're guaranteed to eat 2 hits. And that's 2 hits from each source of AT weaponry - it definitely won't kill the KT, but it makes a dive pretty viable.