Any reason you would play Carnage over Annihilation?
I am the Annihilation Marauder, and I am also one of those people pushing about 2100-2200 dps on tanks. Fully 63, and have all datachrons/companion buffs possible.
I think Ark would run Carnage because he is more comfortable with it (not saying he is incapable of playing annihilation) he just likes the play style and burst damage more. I changed to annihilation after the initial change to gores timing, and I haven't looked back.
I tell you one thing, after all of those attempts, pushing for every inch of dps that you can possibly glean from a fight definitely makes you work out any lingering issues about your spec, or helps you focus on how to play it better.
It's definitely over tuned, but I can agree that I had a fantastic but arduous time during Tanks,