At least part of that behavior is the NVH engineering. Efficiency is sacrificed to an extent so that the engine noise acts more inline with driver expectations.
That's possible. Another factor is that the output of the electrical motor and the storage capacity of the battery is so much smaller than that of the ICE, it tends to get maxed out very quickly, and from that point on the ICE has to modulate the power reserve to respond to the power demand.
I get that the overall emissions are lower in the Karma because the emissions are essentially 0 when the Karma is in electric mode. However, if there is little environmental advantage to having a gas powered engine recharge an electric battery versus power a conventional drivetrain, how is the extended range EV any better than an electric/gas hybrid?
The whole point of the ICE-Generator is to allow you to have a single car for both short and long distance driving so that you could get the EV benefit every day and pay the pollution price only when you absolutely have to. By comparison, a pure EV vehicle never emits any tailpipe emissions but is range-restricted so that you would have to have another car, most likely equipped with an ICE for trips that you know would exceed the EV's maximum range. So depending on your driving patterns, you can either get two cars (or rent an ICE-equipped car when you need it) or get a car such as the Fisker that can fulfill both requirements, but not as efficiently as either a pure EV or a pure ICE car.
Contrary to Fisker propaganda, there is a significant compromise at the heart of the design and that is the dual power source. When you are driving a Fisker in pure EV mode, you are dragging around a 400 LB. motor-generator that serves absolutely no function except dead weight. Likewise, when you have to use the ICE, the 600 LB. battery serves almost no useful purpose other than as a sort of flywheel to smooth out the power changes.
If you made a Karma with just one or the other power source, you would improve the efficiency of operating that power source by itself but then you lose the inherent flexibility of having access to both power sources. So there are no perfect solutions. The Fisker is an attempt to reduce your pollution as much as possible without giving up the option of driving long distances without having to stop for an electrical charge.