Is the Canon EF 11-24mm f/4L USM Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 12mm f/4.5 test image. Observe the contrast and resolution of these results.
Is the Canon EF 11-24mm f/4L USM Lens set to 12mm f/4.5 sharper than the Rokinon SP 10mm f/3.5 Lens set to 10mm f/3.5? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.