I haven't found a single thing mentioning the Havok Nuke in any of the Forerunner Novels. The only encounter Didact had with the Havok Nuke is mentioned above when John used it to destroy the Mantle's Approach and Composer in the end of Halo 4. Didact only survived via escaping via slipspace portal. Having separate keys for Mantle's Approach and the War Sphinx respectively seems alright.
Now that I think about it, I think we should probably remove Cortana's shield from John's profile. She defended him by gathering nearby hard light to form a shield; aka outside help. Plus, as mentioned above, any statistics or abilities that come from Cortana should not be on John's profile and should instead be on Cortana's profile once that gets created. The only Cortana related subject that should be on John's profile is a link to her profile in the equipment section.
That being said, Cortana's tier would best be
Unknow. She herself doesn't actually have combat prowess, but she can hack any nearby computer technology she comes across. Pretty much every feat she has is done by outside help, but her hax and the setting she's in gives her access to it on a standard basis.
Speaking of which, should we remove the nukes from John's profile too? He doesn't actually carry them, and can only use them via outside help. I know
Nova Terra has nukes on her profile, but that's mainly because it's an RTS game where Nuke Silos are often around; and she can summon nukes telekinetically. But John more so has support from the rest of the UNSC. It can still be listed as part of the UNSC Civilization's profile of course, but I think we can all agree that it's not part of John's standard equipment. Though, there are other characters with prep time keys. I'm overall neutral on whether or not they should stay, but would prefer to here what Reppuzan and Soldier Blue think.