I don't want to bring you down, but I think you're being a little overoptimistic on these scenarios, personally.

To wit, consider:

  1. I would have my three rogues obviously stealthed and looking for healer.
  2. I would locate the healer and sprint all my toons to him, just for a sap.
  3. Then shadowstep to the next cloth wearer (or leather).
  4. Rogue1 apply's cheapshot.
Ambush (and all of its pluses) + immediate eviscerate (3 combo points and 15% more dmg)... if i have to, (assasination talents will replenish my energy) backstab (with 40+% more dmg). Ambush, eviscerate, backstab is sure to kill a cloth wearer with 2 rogues ambushing, 3 rogues eviscerate and backstab.
First off, I assume you are going to try to get to #3 above asap, because once you sap everybody's going to be on their guard doing everything they can to flush you out. SS is a little finicky about getting in for some of those SS->ambush/CS/whatever combos in my experience. Maybe your lag is better or something, but it's not a given that I can get that off every time.

But suppose you do, you're looking at the following energy consumption: 10 (SS) + 60 (ambush) + 35 (evis) + [possibly] 60 (bs) = 165 energy. I'll give you two energy ticks (generous), so that brings it back to 125. If Relentless Strikes procs (what other "assassination talents" are you referring to?), and it seems to have a 20% chance the way I'm seeing it (ambushing slaves), you get back to 100. It is possible, but the amount of things that have to happen make it something I wouldn't want to rely on. Take the BS out and you can probably rely on it, but I doubt you're going to be able to time your energy ticks just right after doing all that, so even that's not given.

The achiles heal of all melee boxing teams is positioning. One of the reasons this works as well as it does for us all is that casters don't need fine-grained positioning - pretty good will do. Melee classes, and particularly dagger rogues (probably preeminently so in this game) rely heavily on just that, manuvering yourself to the exact position. I know you've plotted this out in your head in such a way that you feel you can overcome the disadvantages, and good on you. There's a lot of people here, myself close to the top, who'd love to run 5 rogues around for some pvp. I just think you need to remember that ALL pvp is chaotic and you almost NEVER can rely on what you want happening, happening.

That said, I wish you luck and hope it works out well. Keep us posted if you decide to do it.