An exception to Tamron's quality lenses

I was disappointed with this lens and eventually decided to return it. As the title of this brief review states - I hope this lens is the only exception to Tamron's quality lenses.
The cons: 1. Zooming ring is very stiff, so much so that it becomes a real problem; 2. Lack of sharpness, regardless of focusing mode. I shot a few hundred images with this lens and all looked too soft; 3. Most images came out darker or lighter than what you would've expected, regardless of WB or exposure settings. 4. Grainy pictures even in perfect shooting conditions. And lastly there was 0 pop to the images - even a picturesque scene would look dull and flat.
This lens needs to be redesigned from the ground up IMHO.