*UPDATE – Feb 2010*
While mutilate specs are still viable (and sometimes preferred because of the lack of dots you put on your target, Master Poisoner is now the main spec seen in arenas.
Mutilate-prep
Season 6 may have only just begun, but by the looks of it there is one spec dominating the arenas – 41/5/25. It’s early days still, but currently RP is back at the top of 2v2s and RMP is leading the way again 3v3*.
When speccing for mutilate-prep, there is still a large amount of flexibility to be had with point distribution. The choice of filler talents is quite high, so you can really pick a spec to match your team/gear.
41/5/25 seems to deliver decent sustained damage, but if general survival is an issue you may want to put points into Nerves of Steel (possibly even Sleight of Hand if you are are being burst down too fast).
Key talents
Assassination tree
- Puncturing Wounds
- Fleet Footed
- Quick Recovery (if you have a healer ofc)
- Seal Fate
- Deadly Brew
- Mutilate
Combat
- Dual Wield Specialization
Subtlety
- Opportunity
- Dirty Tricks
- Elusiveness
- Heightened Senses
- Preparation
- Dirty Deeds
*source: SK Gaming

Thanks for the spec !