I personally love BoS for solo content, so I'm hoping they don't remove it. Nerf the "removes slowing effects" part and we're good. Didn't it originally remove slowing effects OR grant the speed boost?
Ya MS debuff are 10 % since mid MoP I think in PVP. Deadly Poison better mostly because it lasts 18 seconds and Wound poison lasts 8 seconds. Your venomous wounds procs with rupture when a target is poisoned. Rupture is 23 sec? and Deadly is 18 seconds.
Sin performs really well with multiple targets dotted and with the above mentioned only have to dot other players once every 20 seconds to keep up max damage and max energy regen.
DP is 12 sec duration. Keeping venomous wounds rolling on multiple targs is pretty annoying.