Nightfall Sin Elites...

Shadow Prison-RED ENGINE GO>Black Spider Strike->Twisting Fangs->Black Lotus Strike->Blades Of Steel is better than Horns->Falling in my opinion. I find keeping a target hexed for 2 skill to be easier than looking for a foe not adjacent to another ally. Plus using BLS as your "lead" attack is counter-productive, since you wont recover much energy from it(unless you don't have enough time to recover energy between spikes, but that should rarely happens due to Shadow Prison's 20 seconds recharge).

That's a pretty nice build right there.

But I'd pack some other skill than blades of steel, something like nine tail strike or hoto.

I dunno, I like Blades of steel for the damage it does. Due to people's bad habit of trying to get away when they are snared, almost all of your hits will crit when using SP and I've had BoS hit for 150 dmg total. Now that I think of it though, I think Death Blossom would be a bit better.

Or hoto for the kd/interrupt? Nine Tail Strike if they stanced themselves late or get guardianed? It's just a detail though..

Yeah, they all have something going for them, so everything is fine really.

or just bring 2, and take out a heal if your in TA. Its organized enough that you should expect a stance, and if not, use the other finishing dual attack you brought