The reason why a rogue would use this is because rogues can control the proc easier if it's mainhand, and trust me, it procs a LOT if you have it mainhanded, hence why it got nerfed in the first place.
How'd it get nerfed? Did the proc chance go down?
I know it procs a lot. My friend who I enjoy dueling on a fairly frequent basis has one. ;P
Also, it can still be main-handed. Does its now "One-handed" status effect the proc chance?
Also, if the chance decreases when it's off-handed, I don't understand why. Would it be because of the sinister strikes procing it?
1) Yes.
2) Yeah, it's a cool wepaon to have.
3) I know it can, and no it doesn't.
4) Yes, it does. Same with our "Mace Stun' effect etc. The proc can be controlled more, becuase you're doing a white hit every other second, plus the SS in between, giving it more of a chance to proc. In off-hand it's just going by white hits, and there's a lot less of a chance of knowing when it's going to happen. It doesn't technically decrease its chance of proccing, just it procs more mainhanded.
That's why I don't like to put crippling poison on my offhand, because I know it'll proc better if I have it mainhanded.