Dude, for landscapes Tokina is one awesome choice. As I said earlier, with apertures around 4 to 5.6 you can control some sort of these hot spots in this Tokina. If you see my picture posted above, it is still in a controllable level though I won't say it as the best.
Not really dude, it depends on your focus distance as well. Typically IR people shoot at F8 or F9 because their body may not be calibrated for all their lenses and shooting wide open can show the off focus in the picture. This can be avoided by shooting at low apertures as F8 or F9 but this poses the risk of having a hot spot. You need to be careful in selecting your lens as well..It's a lot of trial and error though..
I always used to think that hotspot is a function of the lens, not of the camera. Its surprising that same lens gives hotspots with some cams, yet no hotspot with others.
Now the question is, whether the 11-16 will give hotspot with 350D. If I can use F4/F5.6 etc., without hotspotting, then its good to go!