Yeah, we really shouldn't treat all Warzone bosses as being equal. I'm only alright with the mechs/vehicles that generally required an Incineration Cannon or Wraith to take out being at High 8-C; and Warden Eternals. Scaling that to anyone else would be reverse power scaling.
As for the Elites, I don't remember them taking hits from Rocket Launchers; aside from maybe on Legendary, but I'm inclined to consider that game mechanics. Dark Nuts aren't High 5-A just because they can take multiple hits from the Master Sword in game. Additionally, Rocket Launchers, Grenades, Spartan Lasers have consistently shown to kill 5 or 6 Spartans in one blow, to Gen 1 scaling to Rocket Launchers is iffy; though, not as iffy as scaling to Wraith Mortars.
However, Small Building level+ for the High Council Elites is reasonable. Tartarus is probably 8-C though, since he's one of the strongest Brute Chieftains and is significantly stronger than Thel, who needed help from Johnson using a Beam Rifle and couldn't really get close to him in combat.
As for the new Incineration Calc, Bambu did give a good point about the timeframe method; that's more so watts rather than joules. That being said, assuming it only took 1 or 2 is really stretching it, and squad can mean almost anything; but note, it's generally safer to use lowballs. Considering that the Gravemind was considered among the Forerunners greatest foes; at least as far as ones that don't require entire fleets, I'm positive they'd be using an army against said foe.
As for the calc itself, I'm still not 100% certain about assuming 15 simultaneous shots vaporized/ionized the entire target instantaneously. It's still possible that they started with the bottom/roots and then bombarded them with multiple shots that each vaporized specific portions. But I'm fine with that low-end 1.14 Kilotons for now at least. But, Warden Eternal is still the only one I'm okay with scaling to and with the At most for the durability, which is what they're rated as now, but we can replace the link.
Also, it's open to discuss here whether or not the Nukes could be re added to the profile. I'm neutral, but leaned towards not having them. But the UNSC civilization profile has them for sure.