Just like how I'm talking I'm assuming you're not suggesting 'just' these mentioned variables, as I imagine polish will end up with a few more (for either of us when talking lol). If so, honestly that is generally the description of the sync yeah.
Only one that worries me slightly was mean time to defeat, unless you are talking about my stagger system suggestion in which case that might be helpful yeah*. But if you're talking about just curving people down and calling it done, I think your first two items are the bigger tickets and probably leave mean time out.
* Stagger system was doing more than just dampening high levels, it would be addressing our ilvling content and creating rewarding gameplay systems for that extra damage. For the intention of keeping time to reward similar but increasing quality time in those contents (so that epic god boss that a player is doing for MSQ still feels cool, but high levels players are not pulling out all their chocobo feathers due to boredom and lack of time value).
Yes I expect a level 10 to have some spells that are technically weaker than the level 100 in unmodified situations be stronger than the level 100 due to the dampening (because those higher level jobs will have other things going on, like ogcds)
I expect the full bar to probably be slightly less damage, though the features may occasionally shine. Since we won't spend time trying to figure out if it's fair that a job can raise, heal, or group speed (healing potency will be dampened like damage, but the feature of it existing- no). We're just focused on algorithmically dampening damage in a way that encourages the player to use their kit in a similar way (so you don't get synced down and suddenly the best choice is to only use the first skill in your combo sequence).
The point to me is definitely not to allow a full kit so the boss is dying even faster, I would argue that would be worse.. but it is to maintain an interesting kit.