OK, just went through the armory so here are my ideas for what to do...
First off, replace those weapons. Get 2x [wowitem=28312]Gladiator's Shanker[/wowitem].
For your spec, get rid of imp ss, get 2x dodge instead, unless of course you think you will be using ss sometimes in arena, but I always preferred dodge with my mutilate build.
Get rid of the 1 point in opportunity and give it to DW specialization.
IMP sprint > endurance. Swap them 2 around.
Why do you have imp. backstab? NO no no, never use backstab with mutilate spec...
2/2 murder 0/3 imp backstab
No fleet footed? you don't use a healer? You don't get kited?
No quick recovery, no master poisoner?
Here is what I would think of a mutilate build...
link It is lacking expose armor, but tried to keep it true to what you took.