I've looked around and haven't seen any discussion on the best way to actually use Murderous Intent, in terms of UI. I realize that everyone's UI is different and so there's a limit on what advice can be offered, but the basic challenge is universal to any rogue who picks up MI.

The ideal solution would be to have a macro that automatically switches to Backstab when the target is below 35%. That's not possible, far as I know. Second to that, it'd be nice to be able to swap your Mutilate button for your Backstab button on command. That's also not possible, at least not during combat. What is possible is swapping entire bars. What I did is to set up Power Auras to notify me when my target is at or below 35% health, and set up a macro (/swapactionbar 1 6). I use Bartender, so I had to go into bars 1 and 6 and enable ActionBar Paging (under State Configuration) for both bars. I made bar 6 a copy of bar 1, except I put my BS macro where my Mut macro is.

The drawback to this approach is that it's not always feasible--on trash mobs, for instance--to swap bars. And of course, you have to have a free bar.

I can't think of another workable solution. You could just plop backstab on your main castbar and start spamming it when your target hits 35%, I guess, but my castbar is already pretty full and the keys I can easily reach during combat--the ones I don't have to take my hands off either my mouse or my movement keys to reach--are largely already full. If anyone's got a better idea, I'd love to hear it.

I don't see the issue with actions bars. I use the default Blizzard UI and map the same keys except Mut/BS on two bars, then Ctrl-1 or Ctrl-2 to switch to the appropriate bar with Mutilate/Backstab. Since we're not a GCD capped class, there's more than enough time to keep an eye on when the boss' health drops below 35%.

There will always be times when it's impossible for one reason or another to be reliably behind the boss (Kologarn, Shade of Aran, etc). For this reason alone you need to be able to choose whether to use Backstab or Mutilate, any solution that uses Backstab to the exclusion of Mutilate under 35% simply won't work.

I have personally been using Instant Deadly Deadly on MH, OH and thrown respectively and I have noticed that I stack deadly poison very fast on mobs.

In theory then, as soon as you have 5 stacks of deadly you should have 3 chances per "hit" from Fok to proc instant poison.

I did a little testing on the training dummies, I found you could proc deadly from the offhand, and from what my addons (classtimer) have shown it was possible to stack 2 stacks of deadly on a single target from a single fok.

I'm not certain of that however, was a little concerned that I may have had some lag applying the first stack and then receiving a second straight away.

Would there be a reliable way to track these procs?

Fractional points of mastery give full benefit. 8.5 mastery will give 1.25% benefit beyond the automatic 8 mastery.

If at some point during a boss fight, I end up with 1, 2 or 3 CP, with only SND up, do I Rupture or do I Mutilate/Backstab till 4+ CP and then Rupture?

Thanks.

Rogue 101 - 4+ finishers. Muti/backstab to gen the extra point(s) to get to 4cp and envenom to refresh SnD if it is about to drop or rupture to get it back and running.

Just the opposite. 1 full point of mastery is 2.5%. So the example of an additional .5 rating giving 1.25% means that you get benefit for every fractional amount put into it.

I haven't seen it discussed but I'm curious which is better for Mut, hRibspreader or hHeartpiece? Just curious if any numbers have been crunched.

EDIT: Feist-Mok corrected me one post down, I had a stupid moment when writing this.
When used on cooldown, max rank Lifeblood is equivalent to 40 static haste rating, or about 88-90 EP (which is probably the weakest dps boost of all professions that give any). Mining, while being a decent source of income, is zero EP.

I am curious about this as well. It's hard to tell for sure without a working spreadsheet, but if we disregard the energy proc, Ribspreader's stats are about 300 EP above the ones found on Heartpierce. So the question now is whether or not the proc is worth 300 EP or more?

The short answer is that it's very very close. During Mutilate they're quite literally indistinguishable. During Backstab, our estimates are less good, but my best guess is that *if* you can spend the extra energy, Heartpierce is better; if you're having any trouble with capping, Rib Spreader is probably safer.