Distance is your main problem, both for the shadows that are being introduced, and for the hot spots.

The Flashbender is doing what it's supposed to do. It makes the light source bigger (not actually big big, but much bigger than the bare speedlight lens) and moves it further away from the camera. As a primary light source, that's enough of an improvement over a naked, straight-ahead camera-mounted flash to be worthwhile when a more suitable bounce can't be achieved (walls or ceilings are too far away or likely to cast bad colours).

As fill, though, it represents a problem. It shares that with every modifier based on "bounce cards" (such as the Lumiquest Big Bounce). Because the source is far away from the lens (typically the bottom of the source will be 12"/30cm from the centre of the lens, and the hot centre of the light source will be several inches/centimetres further away still) you can't actually fill shadows at close distances. The angle is too great. These units are designed to create shadows and shape on your subject, something that direct on-camera flash doesn't ordinarily do.

If your camera has a little beady-eyed pop-up flash, that would be a much better fill source, even as hard as it is, simply because it is so much closer to the axis of the lens. The pop-up may be a horrendous primary light source, but it ain't a half-bad fill at all, especially if it's turned down a stop or two (depending on the camera and the desired result). You can improve that with a diffuser that makes the flash a little bigger (and thus a little softer) without moving it further from the lens. (The Gary Fong Puffer and the Lumiquest Soft Screen are commercial examples of the breed.)

A hot shoe flash firing through a "large" softbox (and let's not kid ourselves, on-camera softboxes aren't actually large) will provide even better results. The bottom of the box usually extends down quite a ways, bringing it closer to the lens, and the size of the softbox is enough to soften the light considerably. (Note: large on-camera softboxes will interfere with the AF-assist beam and the Auto sensor on the flash if they're big enough to bother with. TTL or manual mode will deal with the sensor problem, but you may need the AF assist if you're in a dark environment.) You won't mistake it for a 100cm studio softbox, but it should minimise lines and wrinkles when compared to undiffused flash.

Finally, don't forget that when your subject is very close to a not-very-big light source, the inverse-square law will bite you if you're not friends with it. With something like the Flashbender used from, say, 3 feet away, it's likely that your subjects' faces are receiving about a stop more light than their shoulders. If you're metering the cheek, the nose will be a little hot (that has more to do with the angle of the nose than its prominence) and the forehead will be a lot hot (it is both closer to the flash and likely angled higher than the part of the cheek you're metering from), while the chin, neck and shoulders will be darker than you'd like. That's just how fall-off works, and if you're aware of it you can put that kind of fall-off to good use. (It's not generally a useful thing for fill, though.) Again, bringing the light source closer to the lens will minimize the difference in light-to-subject distance across the subject, and making the light source as big as possible will make the fall-off more linear.