I know what Special Defense Tran does, and I know what I'm saying when I'm suggesting Max HP Max Speed Heatran. There is a reason people run this set, and it is to specifically beat Adamant Max Speed Scizor's.
I dont know what calcs you're talking about, but with just Max HP, Heatran still tanks a ton of special moves in the tier. Granted, making a stupid play like keeping it in vs a pokemon known to carry a super effective move or even Knock Off in Torn-T's case, it contradicts your statement of wanting a healthy, specially defensive heatran. If a Tornadus were to switch in on you, your best bet is to go Clef on the Superpower (which AV Tornadus-T [the more common Tornadus-T variant] heavily prefers to Focus Blast, since Superpower does not have a chance to miss, and straight up OHKOs Scarf Tar after rocks) or the Focus Blast if it's LO. Also, both variants get 2HKO'd regardless by Focus Blast, investment or not.
Lastly, Mega Scizor doesnt need many times to come in and boost vs you. A Mega Scizor team can play so reckless against you as to just set up rocks, maybe a spike, and wait til Kyurem kills a mon so it can scare it out and SD, effectively sealing the game right then and there, as you would have nothing to prevent it from killing Heatran and weakening another member, or from straight up 6-0ing you.
The best part? Kyurem Fusion Bolt on the SD, Azumarill's unboosted Aqua Jet, and Mega Pinsir's quick attack COMBINED cannot OHKO Mega Scizor unless you have SR up. Even then, it's reliant on getting medium to high damage rolls every time.
An easy solution? Put some damn speed on Heatran lol.
