I think the best solution for this kind of issue has to be to sync maximum ilvl down on more content, especially 'max level' dungeons, trials and raids, as they always get outpaced (and made easier than leveling duties) as the post patches add new gear. In addition, for this older content from older expansions, they should be careful to keep old action potencies more balanced with what they were during the era by making use of traits that balance potencies to the correct amount in each level range (like the traits for many jobs at level 84 that increase basic combo action potencies; there should simply be one of these traits for 51-60, 61-70, 71-80 as well affecting all of a job's actions so they're not hitting significantly harder than the content was designed for at the time).

Solving it in this way would also allow first timers to enjoy fights for longer, have a better idea of how the game will play closer to current content and get to experience more of what the boss (and visuals, and music) have to offer before being put back into the MSQ read-grind.

Halicarnassus could also be given the same slapdash fix they gave to Ifrit, (old) Moggle Mog, Leviathan, Ramuh and Shiva Hard/Ex, where the boss simply added an invincibility HP% before the "boss will use their limit break NOW" HP% to prevent overgeared players from killing themselves by skipping their mechanic with too much dps, like Ifrit's Infernal Nails. The downside to this is that the boss basically still dies just as fast and you don't really engage with their mechanics, it's just put in there to stop specifically players having to recognize the issue (not really fair to newer players) and exert self control (hard to do, also, easy to grief). I'd prefer if they didn't do that because these old fights don't need too much to be preserved better, but they've changed a lot of old bosses in ways I didn't prefer, so what's one more...