As much as I think raids on elite should be scaled to their difficulty, I think the way something like Chrono does it is fine. It scales in relation to both quest level and player level.
I think at level, a raid should be a serious challenge for the 12 in it. I don't think a raid that is level 12 should be as challenging for a party of capped 20's as it should be for geared lvl 12's. But having lvl 20's in the same raid with lvl 12s should be harder than it would be if it was all lvl 12's.
For elite chrono, say if you have 12 geared lvl 20's, it should be a fairly easy challenge, except with some boss fights being harder. Cr's relative to the partys level makeup.
Another example, I think TS on elite should be a very hard challenge for lvl 12's geared to lvl 12 awesomeness. But with lvl 20's, it should be pretty easy. The CR's of the mobs should scale up, maybe bring in some different tactics, but since it is a lower end raid, it shouldn't be nearly the challenge as it would be for a lvl 16 raid for the same group.