Zafire, you might want to reconsider your advice. Some of your information is inaccurate.
If I were to spec purely for solo quest-grinding PvE as Mutilate,
this is what I'd do. Filling out DW spec next. Soloing is all about minimizing downtime, make no doubt about it, so that's how I came to those choices. It's also reasonable for instances. You could move points from Deadened Nerves pretty easily (they're kinda "filler") and I didn't take Fleet Footed because being snared isn't a big deal while quest-grinding and rogues will nearly-universally have Cat's Swiftness on their boots, movement speed enhancements do not stack.
For soloing Mutilate you will still stun-lock mobs to decrease incoming damage, lowering downtime and increase XP/hour. CS-Muti-KS-Muti-Envenom. Rinse, repeat.
Eviscerate shows weaker damage than Envenom in Mutilate builds unless talented for. Yes, even considering the down-time of the Deadly Poison stack.
Deadly Poison and Instant Poison are optimal for grinding. Instant goes on the faster dagger. Analysis shows that Fast/Fast daggers are preferred for over-all damage output (esp. with current IP:AP scaling), but be sure to not sacrifice DPS or other stats just to have a faster dagger.
Also: Expertise > Hit (before poison cap) > Agi/AP > Crit > Haste etc.
Other than that, if you really want to excel at Mutilate build (my personal favorite), check out Elitist Jerks which has mostly raid-focussed info, but much of their advice and analysis can be applied to soloing and small-group instancing.
Good luck out there!