being that my main is a full t6 geared rogue and ive been a massive fan of the return of dagger rogues, 51-5-5 has been my spec since 3.0 went live
regarding the OP's cycle for mutilate, i would have to disagree, running a CttC build, the cycle that has been best from my personal experience is as follows:
4-5 SnD (on opener)
4-5 Rupture
*refresh hunger for blood*
4-5 Eviserate (note: before dropping the evis, pool your energy till snd has 3-5 sec remaining)
4-5 Rupture
now, i know alot of rogues have been claiming that envenom is the better route to go, i personally dont agree, being that you lose all your DP stacks every 2nd rotation, your next mutilate will be on a potentially unpoisoned target costing you 50% damage on that mutilate and 3% crit damage bonus with master poisoner
as for the build you posted, i stopped looking at it after i saw Vigor and QR, both of which are pvp talents, not pve
just my 2¢