ShS Daggers works great for lvl 58-59 bgs or for lvl 60 av. Something like
this is want you want to be aiming for at 58. Biggest options are being able to drop a point from Camo & then put the last three into Cheat Death.
You want to take Camo over MoD in ShS dagger builds because being able to one-shot low health players then re-stealth again is vital to your survivability in places like AV. Whilst the full 5/5 aren't needed you need at least 4/5 to be able to re-stealth as soon as combat is dropped from your initial hit. Also, if you are going to be Shadowstepping Into your target, MoD is unnecessary since you will be 25yrs away when you decide to Shs anyway, but the movement speed from Camo will allow you to adjust for enemies who are moving about.
Dirty deeds is great since it will almost guarantee a kill on below ~35% health target with ambush. I used it pre-TBC and found myself able to kill pretty much any target. Premed>Shs>garrote>Backstab(crit)>Rupture will pretty much destroy any opponent at full health.
Keep in mind that people now have easy access to outland gear so you may stumble across the odd warrior or lvl 60 twink/alt (since they are almost synonymous nowadays in the upper brackets because 70s have so much gold from outlands) that has a higher HP pool. Especially now that Highwarlord / Grandmarshall lvl 60 Epic gear is purchasable through honor.
Whilst the build has a fair bit of maneuverability since Shs is now out-of-combat too, there is still the problem of terrible combo point generation that backstab based builds are plagued by. The Shs change somewhat combats this since you no longer
need to throw a kidneyshot in to get off your backstab.
Warriors are particularly vulnerable to this spec at 58-60 lvls since you can Garotte>Rupture them, cripple kite them out until you can either re-stealth or you can ShS again, then ShS>Backstab them whilst they are still trying to get you in intercept range.
This is also one of those limited situations when Remorseless Attacks becomes an option. If you plan on picking people off with one/two shots you can start jumping about the battlefield Ambushing people like a maniac.