Here's a thought - say you're in a raid group and the legendary ring CD is used (selfishly or not) at a time that does not suit your CDs or for a specific mechanic - like say only using it twice in a 5 minute fight instead of 3 times, or for the sake of Mut, completely outside of Vendetta.
The question I pose to theory crafters and the like is: How much of an advantage you think it will be over the 715 ring, at least before we factor in the 3ilvl upgrades from Archi if it never lines up with your CDs?
I guess realistically you'd just have to make your CDs work with it as best you can but I'm thinking this adds a completely new layer of cheese to rankings where some rogues get to line it up with their CDs because they're their guilds ringlord (tm), where others do their best to match their CDs where they can.