I have an LS2 with a cam running 10 degrees of overlap and it has none of the problems you described. It lopes at idle but is very drivable, in fact, I have to fight with my wife just to drive it.

 

One question on this is what factors do you use to determine exhaust size? I have 10 degrees of overlap and a 2.5" exhaust with stock mufflers (duals, Kooks 1 3/4, CATS).

 

Boost cams don't require as much overlap to make power.

Since the plenum is pressurized, there is a good chance the chamber will be
above atmospheric pressure during the overlap period.

That means, IVC tuning and scavenging do not need to be 'excessive' in duration
to achieve good results.

I'm not aware of any boost cams that do not have any overlap. I would think
there is a need for even a few degrees to purge the chamber after each exhaust
stroke.

I'm referring to seat to seat timing when discussing overlap. I would also guess
that overlap duration is proportional to boost level in turbo/supercharged motor.

In other words, the gas speed through the valves at 15 PSI would need much
less time to scavenge the chamber than at 5 PSI (resulting in less overlap).

 

The only turbo cams that are likely to have zero to negative overlap are stock turbo cams like the on an audi. But it is a bandaid trying to compensate for the undersized turbines that they use and the resultant hi exhaust backpressure. This can lead to a situation where the pressure on the exhaust side is higher than the pressure in the intake manifold, if there was any overlap in an engine like this you would just be diluting your intake charge and heating up your intake valve.