I've said it before in these types of threads in the past and I'll say it again:
When the devs already have a system set up for level syncing that keeps moderate balance and is basically future-proofed for every expansion to come, why would they ever waste time designing a new system that is far more complicated and would need constant maintenance everytime the level cap changes when the current one works perfectly for their intentions?
Like, let's take a look at your proposed compromise system.
A level 30 DRK has rampart.
A level 80 DRK has rampart, shadow wall, dark mind, TBN, living dead.
It doesn't matter if you halve the %s on those abilities. A 12% TBN would still negate an entire set of autos from a pack of mobs at level 30, while the level 30 DRK literally has nothing to compete with it. take an 80 WAR vs a 30 one. The 80 WAR has nascent flash. Even if you reduced its lifesteal, it's still more lifesteal than the 30 WAR's zero.
In order to prevent level 80's from shaving 5+mins off of dungeon runs compared to a party of at-level characters, any system designed would have to effectively pretend all those abilities no longer exist (like reducing TBN to 1 HP shield, or reducing OGCds to 1 potency).
And at that point, the ultimate question would need to be asked: what was the point? if you have to gut an 80's kit just to maintain even the smallest semblance of parity, you're no longer playing the same job as you are at 80. All the dev time for nothing. Square makes it clear they want some semblance of balance, so unless you can create a system that:
1) is future proofed for every expansion, without ever needing to modify %s, potencies, etc ever to make it work and keep the same effectiveness
2) can be programmed in about 1 minute (why bother modifying so many skills when the current sync system is literally 1 minute of coding to change a single variable temporarily?)
3) lets you maintain relative parity with a level 15 of your job as a level 80.
Then it stands zero chance of ever being worked on. This topic will continue to be brought up, but the reality is, the current level sync won't be changing. It functions exactly how the devs want it to, its easy to work around with when designing new jobs, and it never has to be changed for future expansions. you can level up and cap tomes without ever needing to touch roulettes; you don't have to touch roulettes unless you want to.