This is something I've been working on for a couple of hours now... but I had the idea for it a few nights ago when I was doing some 1v1's on the Halo 4 ladder. Although a pure ladder can't be possible (yet), because we can't do cross server duels, cross faction duels are possible. So, we can do leader boards for each server. And I'll be doing top 10 world wide based on win ratio in combination with most duels completed. (the exact math is a secret, unless you know math then you can figure out.
So we will know the best 10 hybrid shadows/sins in the world? Awesome.
1v1 is flawed in any mmo unless you are dueling a mirror. I would slaughter my marauder with my scoundrel. I would destroy my marauder with a sniper. I would beat the sniper with a scoundrel and I would beat all of the above as a hybrid sin/shadow.
Not saying you are stupidly overpowered or anything, just saying that a 1v1 ranking is pointless.
Now if you want to do the same thing with 3 v 3? That might be more interesting.
Limit it to 1 tank (guard) and one healer. Could be fun.