Um.... bosses, trash, 5-toons, or soloing?
The habit of relying on rotations from the old days of "Combat or GTFO" doesn't really apply to current Mutilate raiding. We have priorities, not stagnant rotations.
Generally speaking your priorities are SnD > HfB > Rupture. Evis is weaker than Envenom (yes, even when you have a short DP stack). Your goal is to be sure that SnD and HfB never drop and keeping Rupture up as much as is feasible.
I base my boss fights starting with Garrote (often, not always) and a 3+ point SnD to get that started, and then looking at starting a Rupture uptime cycle depending on how much energy I have and how many Combo Points I've accrued.
Shiv pops up occasionally when I'm pooling energy (generally during an Envenom CB cycle) basically to score a cheap combo point but it should never be used in place of Mutilate or a finisher otherwise. Also note that you should never pool Energy waiting to Rupture.
Mutilate is all about resource management and fast, intelligent decision making. You just can't rely on a steady rotation to get you through the entire fight. It's harder than Combat IMO, and that's what I like about it.
As far as your spec: Consider moving 2 points from Relentless to Opportunity and if you have a Retadin in your raid move the points from Master Poisoner to Turn the Tables (their buff pushes ours off). Also the point in Vigor would probably be better in Ruthlessness. But with all spec questions, consult a good spreadsheet for what is optimal.
Hope that helps. Good luck!