Is the Tamron 15-30mm f/2.8 Di VC USD Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 24mm f/2.8 test image. Observe the contrast and resolution of these results.
Is the Tamron 15-30mm f/2.8 Di VC USD Lens set to 24mm f/2.8 sharper than the Zeiss 21mm f/2.8 Classic Lens set to 21mm f/4.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.