its just unburnt oil, sounds like you could use more rtv on the flange.
as long as your jetting is right dont worry about it, and ride it harder.

Very normal, if it blowing out the silencer noticeably then its a problem. The way a 2 stroke works, it dumps fresh un burnt mix out the ex port, then the pipe stuffs it back in before the piston closes off the port. This always leaves a residual coating in the pipe at high oil to gas ratios.
More importantly, there is a Phillips headed screw on the left side case ahead of the stator. Put a tray or rag under rit and remove the screw. It should drip a little oil. If it runs out, you need to look at you jetting for sure. But not necessarilly if the pipe leaks a little at the first two joints.

The black goo is a good sign that the engine is getting lubrication all of the way through the engine.  The only oil the engine gets, is what is put in the gasoline.  The oil  you pour in the side of the engine only lubricates the transmission.

No smoke or no goo may be a sign of lack of lubrication unless your engine always runs at full throttle and high RPM. 

A two stroke engine running 15:1 fuel to oil ratio when running at sustained high RPM and full throttle will make very little smoke and no goo.  The inside of the silencer will be dry and almost soot free after a hard dyno session.