UWA lenses are interesting, I personally feel like people get way to caught up in the canon 10-22. Don't get me wrong it is a fantastic lens, it focus'es super fast, its always spot on, the flare is nearly non existent, and the lens is tack sharp wide open. However, I don't know of many landscapes I have ever shot where I wasn't on a tripod if possible, and stopped down to f8 or even f11, not to mention I probably focused manually in live view. If you are thinking of doing these things then consider a tokina, sigma, or tamron. Personally I decided my 17-40mm wasn't wide enough for me, and I couldn't justify the cost of a 14 2.8 from canon, so I went with one of the popular rokinon/samyang/bower/vivitar 14 2.8 manual lenses. I have absolutely loved the lens so far. Anyhow my point is save the money and get a lens that will force you to spend a second longer on the shot, the results will not disappoint.
If you were thinking of spending as much as 1500 on a 16-35, and you instead put that money towards maybe a bower 14mm 2.8 for around 360, you would be left with 1100 to maybe purchase a second land 300 F4 L IS, or maybe a 70-200 F4 both can be used as fantastic nature lenses and all around great items to have in a bag. A 70-200 F4 and a 14 2.8 Bower could be had for under 1000 if you find a good deal, those 2 lenses could give you a pretty healthy range that would allow you to possibly drop the 55-250 and 70-300 from you bag and bump up the quality a bit to.