While I see some issues on DPS skills, the bigger ones I see are on tanks and healers. Say an at-level tank only has Rampart for 20% reduction, while an over-leveled tank also has its 40% reduction. How do you deal with that? If you don't make any adjustments, then it inevitably becomes a liability having the at-level tank, which is exactly the primary goal SE is trying to avoid. If you do adjust it so that the over-leveled tank has to use both of its abilities to achieve the 20% reduction, then what was the point even keeping them both? And that's not even factoring the even higher-leveled tanks that will have their full immunity...

Same with healers. What do you with a WHM that has Benediction vs. one that doesn't? You can't "adjust the potency" of a 100% heal. Either you have it or you don't.

Remember, one of SE's biggest objectives with their system is to ensure that lower-level players (or rather *at* level players) don't get harassed because they're a liability compared to having a higher-level player. Until you can ensure any "sync" system you propose doesn't directly or indirectly encourage this, it's a non-starter.