^Related^
it's what you prefer really, I tend to switch around a lot of my melee weapons when I run spy2.0 with loki for rep. Faster weapons are usually more fun.
First, I just started using Dual Ichors and have only been interested in Warframe stealth for the last few days. In other words, take this with as much salt as you want. Long story short: yes. Long story kept long: Since the Dual Ichors have a high crit chance and extremely high crit damage, I'd consider it viable as long as you build for crits. I'm not sure if crits are counted into stealth backstabs, but they usually kill automatically anyway, correct me if I'm wrong. Also, if you are seen, I've noticed that the Dual Ichors are pretty effective for "drilling through crowds", as I call it. However, since the Dual Ichors are dual swords, they take up a lot of stamina, which has screwed me a few times while "drilling". Because of this, I suggest you put Quick Rest and/or Marathon to keep stamina ready. This can also help you run from a bad situation. Once again, take this with as much salt as you want. I hope it helps.