"Dark Briar Barrage - saves me the pain of having to run behind a Trojan to poke it to death, and it works like a Nitronome without knockback and flash (given that zombies are neutral to piercing)."

I just did this not 20 mins ago.. because I've always wondered what it was like and if it was viable based on similar assumptions you've made. Suffice it to say that it didn't work as all as I envisioned. It does close to 200 dmg per zombie per hit for neutral damage.

Okay, it might do better on the trojans right? RIGHT? No. It just deals about 260 or was it 270 per trojan per hit. (without dmg UV)
Do you remember how a DBB works? Yes it has a super long fuse. Okay. Do you remember how a trojan works? Yeap, you have to poke it in the back. Ok, so in order to hit it with the DBB, you basically have to go around and around the trojan in circles. Because you know, one lay only hits them once. Plus you have to circle it once... rather freeze and poke. Keep in mind that I had Ultra CTR on mine and I was already extremely bored.

I felt like I was on a merry go round and the trojans were the axel. Took around 12 spins or more to kill them both. I lol'ed.

And this was when I was soloing the room... imagine the swordies coming in, you'd miss most of the time.

In other cases, you might say, okay the DPS stacks up in high zombie density areas right? Not really... since it has no knockback (something that is needed in FSC, even just a little bit), and a supa long fuse, you're vunerable for way too long D; Even with full Mad Bomber I don't see it working out.. plus slags are going to be literally breathing down your neck all the time... and setting you on fire.

I also tried it on the rooms in D26/27. The only part where it might seem at all significant is the wolver room in 27. But err. Yea you get the idea.
In the last room it doesn't work at all :< disappointing damage and whatnot.

My team called it "the troll bomb". And I'd have to agree.

I'd give my vote to the VT just because out of those options it is what I bring... all the time.

The damage from the VT really stacks and it works like a shiver.. except with a (surprisingly high) DOT. I feel as if even though the EV is a good choice too, there are too few places in FSC you can really use it to its full potential. I've found that EV only works well at the beginning of rooms, but not during (exception is the zombie wave room, but that is at the start of waves only as well). Whereas for a VT you can use it anytime anywhere, and not disrupt the swordies from spamming (plus you can take it into lockdown too)!

Also.. you know how sometimes you need to shield bump zombies? Well.. a VT allows you to do that while killing it, while a shiver doesn't :< Since ... you know... the zombies are FROZEN in place.

The VT is ABSOLUTELY worth the weapon slot... very versatile. It's the bomb I lay first before starting any room. I'm almost to the point where I don't bring shiver if I'm not the shiverer at Vana.

And the most important thing about VT: It keeps on damaging even when you're using DA or whatever else you're using. Every other option has you running left to right, yet VT does all the work for you: Passes shock for you, keeps on damaging.

On the Nitro:- You're correct in that it is absolutely great for Solo play. All about the knockback, even though the damage is only 200 per xD
My solo FSC weapons are: Glacius, Levi, Nitro, Shiver.

Despite people saying it is a major nuisaince, I have seen it used effectively as a group in FSC. Have you ever tried 3-4 nitros and doing the 4-corners-key-in-the-middle room? Cleans out in record time with maximum laziness ++++ Although you'd need really good friends for that xD

I can't comment on the RSS because I've never used it firsthand, but I also know that it does 200/shard/zombie hit. I found it quite difficult not to hack n' slash at the RSS guy trying to position it just right (and still only hit it with one shard).

TL;DR, get VT for versatility and max DOT.