I disagree with passive. It is not passive in D&D. The player can choose which attack they want to use Sneak Attack if doing 2 weapons. It can either be used in primary or off hand.
A toggle is really the only way to make it work properly. Default toggle is primary hand. Then yes. Every hit is with Sneak Attack with primary hand. If using 2 weapons, you can toggle to Secondary and when you hit your off hand gets Sneak Attack.
Right now, though, it is a skill, and I agree it doesn't work well. You can't use it as off hand, you can easily forget to use it, and you can't combine it with other things.
Geez. Imagine dual classing Fighter/Rogue. Sneak Attack + Combat Maneuvers. Nope. You can't select both at once. One or the other.
