Absolutely agree. I started a forum topic on this very subject a few months ago asking who was using the Nikon 14-24 on Canon EOS.
Waiting for Canon to develop, test, manufacture and deliver on a new product is a missed opportunity. I've got the 16-35 and 24TSE II and Zeiss 35mm for landscape, but I really need an ultra wide.
I just returned the new Sigma 12-24 II for Canon. Big mistake on my part, the corners are still soft and un-usable in my opinion. The Samyang 14 is calling me but I need an adapter with a chip for focus confirmation.
What has your research found for UWA? ...besides 14-24?
5D3, 1D4, 16-35 2.8L ll, 50 1.2L, 50 1.4, 24-70 2.8L II, 135 F2.0L, 200 F2.8L ll, 70-200 2.8L II, 70-300L, 100-400L, 24 TSE L II, 85 1.2L II, 100 2.8L, ZEISS 100 2.0, ZE 50 2.0, ZE 35 2.0, ROKONON 35 1.4, SIGMA 35mm f1.4, S110, S100, sony RX-100 and one big-a$$ bag